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How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates, and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and its scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position your work in relation to other researchers and theorists
  • Show how your research addresses a gap or contributes to a debate
  • Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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methods for a literature review

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models, and methods?
  • Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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methods for a literature review

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

  • Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically evaluate: mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

  • Sampling methods
  • Simple random sampling
  • Stratified sampling
  • Cluster sampling
  • Likert scales
  • Reproducibility

 Statistics

  • Null hypothesis
  • Statistical power
  • Probability distribution
  • Effect size
  • Poisson distribution

Research bias

  • Optimism bias
  • Cognitive bias
  • Implicit bias
  • Hawthorne effect
  • Anchoring bias
  • Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarize yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

  • An introductory paragraph that explains what your working topic and thesis is
  • A forecast of key topics or texts that will appear in the review
  • Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
  • Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically Evaluate: Mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

  • Summarize the key findings you have taken from the literature and emphasize their significance
  • Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

  • Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
  • Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
  • Qualitative versus quantitative research
  • Empirical versus theoretical scholarship
  • Divide the research by sociological, historical, or cultural sources
  • Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

  • It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
  • Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
  • Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
  • Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

  • Explains the background of research on a topic.
  • Demonstrates why a topic is significant to a subject area.
  • Discovers relationships between research studies/ideas.
  • Identifies major themes, concepts, and researchers on a topic.
  • Identifies critical gaps and points of disagreement.
  • Discusses further research questions that logically come out of the previous studies.

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1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

  • Make sure your research question is not too broad or too narrow.  Is it manageable?
  • Begin writing down terms that are related to your question. These will be useful for searches later.
  • If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

  • This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

  • use the tabs on this guide
  • Find other databases in the Nursing Information Resources web page
  • More on the Medical Library web page
  • ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

  • Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
  • Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
  • Review the abstracts of research studies carefully. This will save you time.
  • Use the bibliographies and references of research studies you find to locate others.
  • Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
  • Ask your librarian for help at any time.
  • Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

  • What was the research question of the study you are reviewing? What were the authors trying to discover?
  • Was the research funded by a source that could influence the findings?
  • What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
  • Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
  • If there are conflicting studies, why do you think that is?
  • How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

  • Review the abstracts carefully.  
  • Keep careful notes so that you may track your thought processes during the research process.
  • Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Encyclopedia of Evidence in Pharmaceutical Public Health and Health Services Research in Pharmacy pp 1–15 Cite as

Methodological Approaches to Literature Review

  • Dennis Thomas 2 ,
  • Elida Zairina 3 &
  • Johnson George 4  
  • Living reference work entry
  • First Online: 09 May 2023

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The literature review can serve various functions in the contexts of education and research. It aids in identifying knowledge gaps, informing research methodology, and developing a theoretical framework during the planning stages of a research study or project, as well as reporting of review findings in the context of the existing literature. This chapter discusses the methodological approaches to conducting a literature review and offers an overview of different types of reviews. There are various types of reviews, including narrative reviews, scoping reviews, and systematic reviews with reporting strategies such as meta-analysis and meta-synthesis. Review authors should consider the scope of the literature review when selecting a type and method. Being focused is essential for a successful review; however, this must be balanced against the relevance of the review to a broad audience.

  • Literature review
  • Systematic review
  • Meta-analysis
  • Scoping review
  • Research methodology

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Noyes J, Booth A, Flemming K, et al. Cochrane qualitative and implementation methods group guidance series – paper 3: methods for assessing methodological limitations, data extraction and synthesis, and confidence in synthesized qualitative findings. J Clin Epidemiol. 2018a;97:49–58.

Noyes J, Booth A, Moore G, Flemming K, Tunçalp Ö, Shakibazadeh E. Synthesising quantitative and qualitative evidence to inform guidelines on complex interventions: clarifying the purposes, designs and outlining some methods. BMJ Glob Health. 2019;4(Suppl 1):e000893.

Peters MD, Godfrey CM, Khalil H, McInerney P, Parker D, Soares CB. Guidance for conducting systematic scoping reviews. Int J Evid Healthcare. 2015;13(3):141–6.

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Centre of Excellence in Treatable Traits, College of Health, Medicine and Wellbeing, University of Newcastle, Hunter Medical Research Institute Asthma and Breathing Programme, Newcastle, NSW, Australia

Dennis Thomas

Department of Pharmacy Practice, Faculty of Pharmacy, Universitas Airlangga, Surabaya, Indonesia

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Thomas, D., Zairina, E., George, J. (2023). Methodological Approaches to Literature Review. In: Encyclopedia of Evidence in Pharmaceutical Public Health and Health Services Research in Pharmacy. Springer, Cham. https://doi.org/10.1007/978-3-030-50247-8_57-1

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Research Methods: Literature Reviews

  • Annotated Bibliographies
  • Literature Reviews
  • Scoping Reviews
  • Systematic Reviews
  • Scholarship of Teaching and Learning
  • Persuasive Arguments
  • Subject Specific Methodology

A literature review involves researching, reading, analyzing, evaluating, and summarizing scholarly literature (typically journals and articles) about a specific topic. The results of a literature review may be an entire report or article OR may be part of a article, thesis, dissertation, or grant proposal. A literature review helps the author learn about the history and nature of their topic, and identify research gaps and problems.

Steps & Elements

Problem formulation

  • Determine your topic and its components by asking a question
  • Research: locate literature related to your topic to identify the gap(s) that can be addressed
  • Read: read the articles or other sources of information
  • Analyze: assess the findings for relevancy
  • Evaluating: determine how the article are relevant to your research and what are the key findings
  • Synthesis: write about the key findings and how it is relevant to your research

Elements of a Literature Review

  • Summarize subject, issue or theory under consideration, along with objectives of the review
  • Divide works under review into categories (e.g. those in support of a particular position, those against, those offering alternative theories entirely)
  • Explain how each work is similar to and how it varies from the others
  • Conclude which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of an area of research

Writing a Literature Review Resources

  • How to Write a Literature Review From the Wesleyan University Library
  • Write a Literature Review From the University of California Santa Cruz Library. A Brief overview of a literature review, includes a list of stages for writing a lit review.
  • Literature Reviews From the University of North Carolina Writing Center. Detailed information about writing a literature review.
  • Undertaking a literature review: a step-by-step approach Cronin, P., Ryan, F., & Coughan, M. (2008). Undertaking a literature review: A step-by-step approach. British Journal of Nursing, 17(1), p.38-43

methods for a literature review

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Systematic Reviews: Types of literature review, methods, & resources

  • Types of literature review, methods, & resources
  • Protocol and registration
  • Search strategy
  • Medical Literature Databases to search
  • Study selection and appraisal
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Analytical reviews

GUIDELINES FOR HOW TO CARRY OUT AN ANALYTICAL REVIEW OF QUANTITATIVE RESEARCH

Enhancing the QUAlity and Transparency Of health Research (EQUATOR) network. (Tracking and listing over 550 reporting guidelines for various different study types including Randomised trials, Systematic reviews, Study protocols, Diagnostic/prognostic studies, Case reports, Clinical practice guidelines, Animal pre-clinical studies, etc). http://www.equator-network.org/resource-centre/library-of-health-research-reporting/

When comparing therapies :

PRISMA (Guideline on how to perform and write-up a systematic review and/or meta-analysis of the outcomes reported in multiple clinical trials of therapeutic interventions. PRISMA  replaces the previous QUORUM statement guidelines ):  Liberati, A,, Altman, D,, Moher, D, et al. (2009). The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration.  Plos Medicine, 6 (7):e1000100. doi:10.1371/journal.pmed.1000100 

When comparing diagnostic methods :

STAndards for the Reporting of Diagnostic accuracy studies (STARD) Statement. (Reporting guidelines for writing up a study comparing the accuracy of competing diagnostic methods)  http://www.stard-statement.org/

When evaluating clinical practice guidelines :

AGREE Research Trust (ART) (2013).  Appraisal of Guidelines for Research & Evaluation (AGREE-II) . (A 23-item instrument for as sessing th e quality of Clinical Practice Guidelines. Used internationally for evaluating or deciding which guidelines could be recommended for use in practice or to inform health policy decisions.)

National Guideline Clearinghouse Extent of Adherence to Trustworthy Standards (NEATS) Instrument (2019). (A 15-item instrument using scales of 1-5 to evaluate a guideline's adherence to the Institute of Medicine's standard for trustworthy guidelines. It has good external validity among guideline developers and good interrater reliability across trained reviewers.)

When reviewing genetics studies

Human genetics review reporting guidelines.  Little J, Higgins JPT (eds.). The HuGENet™ HuGE Review Handbook, version 1.0 . 

When you need to re-analyze individual participant data

If you wish to collect, check, and re-analyze individual participant data (IPD) from clinical trials addressing a particular research question, you should follow the  PRISMA-IPD  guidelines as reported in  Stewart, L.A., Clarke, M., Rovers, M., et al. (2015). Preferred Reporting Items for a Systematic Review and Meta-analysis of Individual Participant Data: The PRISMA-IPD Statement. JAMA, 313(16):1657-1665. doi:10.1001/jama.2015.3656 .

When comparing Randomized studies involving animals, livestock, or food:

O’Connor AM, et al. (2010).  The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety by modifying the CONSORT statement.  Zoonoses Public Health. 57(2):95-104. Epub 2010/01/15. doi: 10.1111/j.1863-2378.2009.01311.x. PubMed PMID: 20070653.

Sargeant JM, et al. (2010).  The REFLECT Statement: Reporting Guidelines for Randomized Controlled Trials in Livestock and Food Safety: Explanation and Elaboration.  Zoonoses Public Health. 57(2):105-36. Epub 2010/01/15. doi: JVB1312 [pii] 10.1111/j.1863-2378.2009.01312.x. PubMed PMID: 20070652.

GUIDELINES FOR HOW TO WRITE UP FOR PUBLICATION THE RESULTS OF ONE QUANTITATIVE CLINICAL TRIAL

When reporting the results of a Randomized Controlled Trial :

Consolidated Standards of Reporting Trials (CONSORT) Statement. (2010 reporting guideline for writing up a Randomized Controlled Clinical Trial).  http://www.consort-statement.org . Since updated in 2022, see Butcher, M. A., et al. (2022). Guidelines for Reporting Outcomes in Trial Reports: The CONSORT-Outcomes 2022 Extension . JAMA : the Journal of the American Medical Association, 328(22), 2252–2264. https://doi.org/10.1001/jama.2022.21022

Kilkenny, C., Browne, W. J., Cuthill, I. C., Emerson, M., & Altman, D. G. (2010). Improving bioscience research reporting: The ARRIVE guidelines for reporting animal research. PLoS Biology, 8(6), e1000412–e1000412. https://doi.org/10.1371/journal.pbio.1000412 (A 20-item checklist, following the CONSORT approach, listing the information that published articles reporting research using animals should include, such as the number and specific characteristics of animals used; details of housing and husbandry; and the experimental, statistical, and analytical methods used to reduce bias.)

Narrative reviews

GUIDELINES  FOR HOW TO CARRY OUT  A  NARRATIVE REVIEW / QUALITATIVE RESEARCH /  OBSERVATIONAL STUDIES

Campbell, M. (2020). Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline. BMJ, 368. doi: https://doi.org/10.1136/bmj.l6890  (guideline on how to analyse evidence for a narrative review, to provide a recommendation based on heterogenous study types).

Community Preventive Services Task Force (2021).  The Methods Manual for Community Guide Systematic Reviews . (Public Health Prevention systematic review guidelines)

Enhancing the QUAlity and Transparency Of health Research (EQUATOR) network. (Tracking and listing over 550 reporting guidelines for various different study types including Observational studies, Qualitative research, Quality improvement studies, and Economic evaluations). http://www.equator-network.org/resource-centre/library-of-health-research-reporting/

Cochrane Qualitative & Implementation Methods Group. (2019). Training resources. Retrieved from  https://methods.cochrane.org/qi/training-resources . (Training materials for how to do a meta-synthesis, or qualitative evidence synthesis). 

Cornell University Library (2019). Planning worksheet for structured literature reviews. Retrieved 4/8/22 from  https://osf.io/tnfm7/  (offers a framework for a narrative literature review).

Green, B. N., Johnson, C. D., & Adams, A. (2006).  Writing narrative literature reviews for peer-reviewed journals: secrets of the trade . Journal of Chiropractic Medicine, 5(3): 101-117. DOI: 10.1016/ S0899-3467 (07)60142-6.  This is a very good article about what to take into consideration when writing any type of narrative review.

When reviewing observational studies/qualitative research :

STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement. (Reporting guidelines for various types of health sciences observational studies).  http://www.strobe-statement.org 

Meta-analysis of Observational Studies in Epidemiology (MOOSE)  http://jama.jamanetwork.com/article.aspx?articleid=192614

RATS Qualitative research systematic review guidelines.  https://www.equator-network.org/reporting-guidelines/qualitative-research-review-guidelines-rats/

Methods/Guidance

Right Review , this decision support website provides an algorithm to help reviewers choose a review methodology from among 41 knowledge synthesis methods.

The Systematic Review Toolbox , an online catalogue of tools that support various tasks within the systematic review and wider evidence synthesis process. Maintained by the UK University of York Health Economics Consortium, Newcastle University NIHR Innovation Observatory, and University of Sheffield School of Health and Related Research.

Institute of Medicine. (2011).  Finding What Works in Health Care: Standards for Systematic Reviews . Washington, DC: National Academies  (Systematic review guidelines from the Health and Medicine Division (HMD) of the U.S. National Academies of Sciences, Engineering, and Medicine (formerly called the Institute of Medicine)).

International Committee of Medical Journal Editors (2022).  Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly work in Medical Journals . Guidance on how to prepare a manuscript for submission to a Medical journal.

Cochrane Handbook of Systematic Reviews of Interventions (International Cochrane Collaboration systematic review guidelines). The various Cochrane review groups comporise around 30,000 physicians around the world working in the disciplines on reviews of interventions with very detailed methods for verifying the validity of the research methods and analysis performed in screened-in Randmized Controlled Clinical Trials. Typically published Cochrane Reviews are the most exhaustive review of the evidence of effectiveness of a particular drug or intervention, and include a statistical meta-analysis. Similar to practice guidelines, Cochrane reviews are periodically revised and updated.

Joanna Briggs Institute (JBI) Manual of Evidence Synthesis . (International systematic review guidelines). Based at the University of Adelaide, South Australia, and collaborating with around 80 academic and medical entities around the world. Unlike Cochrane Reviews that strictly focus on efficacy of interventions, JBI offers a broader, inclusive approach to evidence, to accommodate a range of diverse questions and study designs. The JBI manual provides guidance on how to analyse and include both quantitative and qualitative research.

Cochrane Methods Support Unit, webinar recordings on methodological support questions 

Cochrane Qualitative & Implementation Methods Group. (2019). Training resources. Retrieved from https://methods.cochrane.org/qi/training-resources . (How to do a meta-synthesis, or qualitative evidence synthesis). 

Center for Reviews and Dissemination (University of York, England) (2009).  Systematic Reviews: CRD's guidance for undertaking systematic reviews in health care . (British systematic review guidelines). 

Agency for Health Research & Quality (AHRQ) (2013). Methods guide for effectiveness and comparative effectiveness reviews . (U.S. comparative effectiveness review guidelines)

Hunter, K. E., et al. (2022). Searching clinical trials registers: guide for systematic reviewers.  BMJ (Clinical research ed.) ,  377 , e068791. https://doi.org/10.1136/bmj-2021-068791

Patient-Centered Outcomes Research Institute (PCORI).  The PCORI Methodology Report . (A 47-item methodology checklist for U.S. patient-centered outcomes research. Established under the Patient Protection and Affordable Care Act, PCORI funds the development of guidance on the comparative effectivess of clinical healthcare, similar to the UK National Institute for Clinical Evidence but without reporting cost-effectiveness QALY metrics). 

Canadian Agency for Drugs and Technologies in Health (CADTH) (2019). Grey Matters: a practical tool for searching health-related grey literature. Retrieved from https://www.cadth.ca/resources/finding-evidence/grey-matters . A checklist of N American & international online databases and websites you can use to search for unpublished reports, posters, and policy briefs, on topics including general medicine and nursing, public and mental health, health technology assessment, drug and device regulatory, approvals, warnings, and advisories.

Hempel, S., Xenakis, L., & Danz, M. (2016). Systematic Reviews for Occupational Safety and Health Questions: Resources for Evidence Synthesis. Retrieved 8/15/16 from http://www.rand.org/pubs/research_reports/RR1463.html . NIOSH guidelines for how to carry out a systematic review in the occupational safety and health domain.

A good source for reporting guidelines is the  NLM's  Research Reporting Guidelines and Initiatives .

Grading of Recommendations Assessment, Development and Evaluation (GRADE). (An international group of academics/clinicians working to promote a common approach to grading the quality of evidence and strength of recommendations.) 

Phillips, B., Ball, C., Sackett, D., et al. (2009). Oxford Centre for Evidence Based Medicine: Levels of Evidence. Retrieved 3/20/17 from https://www.cebm.net/wp-content/uploads/2014/06/CEBM-Levels-of-Evidence-2.1.pdf . (Another commonly used criteria for grading the quality of evidence and strength of recommendations, developed in part by EBM guru David Sackett.) 

Systematic Reviews for Animals & Food  (guidelines including the REFLECT statement for carrying out a systematic review on animal health, animal welfare, food safety, livestock, and agriculture)

Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies . Health Information & Libraries Journal, 26(2), 91-108. doi:10.1111/j.1471-1842.2009.00848.x. (Describes 14 different types of literature and systematic review, useful for thinking at the outset about what sort of literature review you want to do.)

Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Meeting the review family: exploring review types and associated information retrieval requirements . Health information and libraries journal, 36(3), 202–222. doi:10.1111/hir.12276  (An updated look at different types of literature review, expands on the Grant & Booth 2009 article listed above).

Garrard, J. (2007).  Health Sciences Literature Review Made Easy: The Matrix Method  (2nd Ed.).   Sudbury, MA:  Jones & Bartlett Publishers. (Textbook of health sciences literature search methods).

Zilberberg, M. (2012).  Between the lines: Finding the truth in medical literature . Goshen, MA: Evimed Research Press. (Concise book on foundational concepts of evidence-based medicine).

Lang, T. (2009). The Value of Systematic Reviews as Research Activities in Medical Education . In: Lang, T. How to write, publish, & present in the health sciences : a guide for clinicians & laboratory researchers. Philadelphia : American College of Physicians.  (This book chapter has a helpful bibliography on systematic review and meta-analysis methods)

Brown, S., Martin, E., Garcia, T., Winter, M., García, A., Brown, A., Cuevas H.,  & Sumlin, L. (2013). Managing complex research datasets using electronic tools: a meta-analysis exemplar . Computers, Informatics, Nursing: CIN, 31(6), 257-265. doi:10.1097/NXN.0b013e318295e69c. (This article advocates for the programming of electronic fillable forms in Adobe Acrobat Pro to feed data into Excel or SPSS for analysis, and to use cloud based file sharing systems such as Blackboard, RefWorks, or EverNote to facilitate sharing knowledge about the decision-making process and keep data secure. Of particular note are the flowchart describing this process, and their example screening form used for the initial screening of abstracts).

Brown, S., Upchurch, S., & Acton, G. (2003). A framework for developing a coding scheme for meta-analysis . Western Journal Of Nursing Research, 25(2), 205-222. (This article describes the process of how to design a coded data extraction form and codebook, Table 1 is an example of a coded data extraction form that can then be used to program a fillable form in Adobe Acrobat or Microsoft Access).

Elamin, M. B., Flynn, D. N., Bassler, D., Briel, M., Alonso-Coello, P., Karanicolas, P., & ... Montori, V. M. (2009). Choice of data extraction tools for systematic reviews depends on resources and review complexity .  Journal Of Clinical Epidemiology ,  62 (5), 506-510. doi:10.1016/j.jclinepi.2008.10.016  (This article offers advice on how to decide what tools to use to extract data for analytical systematic reviews).

Riegelman R.   Studying a Study and Testing a Test: Reading Evidence-based Health Research , 6th Edition.  Lippincott Williams & Wilkins, 2012. (Textbook of quantitative statistical methods used in health sciences research).

Rathbone, J., Hoffmann, T., & Glasziou, P. (2015). Faster title and abstract screening? Evaluating Abstrackr, a semi-automated online screening program for systematic reviewers. Systematic Reviews, 480. doi:10.1186/s13643-015-0067-6

Guyatt, G., Rennie, D., Meade, M., & Cook, D. (2015). Users' guides to the medical literature (3rd ed.). New York: McGraw-Hill Education Medical.  (This is a foundational textbook on evidence-based medicine and of particular use to the reviewer who wants to learn about the different types of published research article e.g. "what is a case report?" and to understand what types of study design best answer what types of clinical question).

Glanville, J., Duffy, S., Mccool, R., & Varley, D. (2014). Searching ClinicalTrials.gov and the International Clinical Trials Registry Platform to inform systematic reviews: what are the optimal search approaches? Journal of the Medical Library Association : JMLA, 102(3), 177–183. https://doi.org/10.3163/1536-5050.102.3.007

Ouzzani, M., Hammady, H., Fedorowicz, Z., & Elmagarmid, A. (2016). Rayyan a web and mobile app for systematic reviews.  Systematic Reviews, 5 : 210, DOI: 10.1186/s13643-016-0384-4. http://rdcu.be/nzDM

Kwon Y, Lemieux M, McTavish J, Wathen N. (2015). Identifying and removing duplicate records from systematic review searches. J Med Libr Assoc. 103 (4): 184-8. doi: 10.3163/1536-5050.103.4.004. https://www.ncbi.nlm.nih.gov/pubmed/26512216

Bramer WM, Giustini D, de Jonge GB, Holland L, Bekhuis T. (2016). De-duplication of database search results for systematic reviews in EndNote. J Med Libr Assoc. 104 (3):240-3. doi: 10.3163/1536-5050.104.3.014. Erratum in: J Med Libr Assoc. 2017 Jan;105(1):111. https://www.ncbi.nlm.nih.gov/pubmed/27366130

McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. J Clin Epidemiol. 2016;75:40–46. doi: 10.1016/j.jclinepi.2016.01.021 . PRESS is a guideline with a checklist for librarians to critically appraise the search strategy for a systematic review literature search.

Clark, JM, Sanders, S, Carter, M, Honeyman, D, Cleo, G, Auld, Y, Booth, D, Condron, P, Dalais, C, Bateup, S, Linthwaite, B, May, N, Munn, J, Ramsay, L, Rickett, K, Rutter, C, Smith, A, Sondergeld, P, Wallin, M, Jones, M & Beller, E 2020, 'Improving the translation of search strategies using the Polyglot Search Translator: a randomized controlled trial',  Journal of the Medical Library Association , vol. 108, no. 2, pp. 195-207.

Journal articles describing systematic review methods can be searched for in PubMed using this search string in the PubMed search box: sysrev_methods [sb] . 

Software tools for systematic reviews

  • Covidence GW in 2019 has bought a subscription to this Cloud based tool for facilitating screening decisions, used by the Cochrane Collaboration. Register for an account.
  • NVIVO for analysis of qualitative research NVIVO is used for coding interview data to identify common themes emerging from interviews with several participants. GW faculty, staff, and students may download NVIVO software.
  • RedCAP RedCAP is software that can be used to create survey forms for research or data collection or data extraction. It has very detailed functionality to enable data exchange with Electronic Health Record Systems, and to integrate with study workflow such as scheduling follow up reminders for study participants.
  • Systematic Review Toolbox Select the Healthcare discipline and features you want a tool to support.
  • SRDR tool from AHRQ Free, web-based and has a training environment, tutorials, and example templates of systematic review data extraction forms
  • RevMan 5 RevMan 5 is the desktop version of the software used by Cochrane systematic review teams. RevMan 5 is free for academic use and can be downloaded and configured to run as stand alone software that does not connect with the Cochrane server if you follow the instructions at https://training.cochrane.org/online-learning/core-software-cochrane-reviews/revman/revman-5-download/non-cochrane-reviews
  • Rayyan Free, web-based tool for collecting and screening citations. It has options to screen with multiple people, masking each other.
  • GradePro Free, web application to create, manage and share summaries of research evidence (called Evidence Profiles and Summary of Findings Tables) for reviews or guidelines, uses the GRADE criteria to evaluate each paper under review.
  • DistillerSR Needs subscription. Create coded data extraction forms from templates.
  • EPPI Reviewer Needs subscription. Like DistillerSR, tool for text mining, data clustering, classification and term extraction
  • SUMARI Needs subscription. Qualitative data analysis.
  • Dedoose Needs subscription. Qualitative data analysis, similar to NVIVO in that it can be used to code interview transcripts, identify word co-occurence, cloud based.
  • Meta-analysis software for statistical analysis of data for quantitative reviews SPSS, SAS, and STATA are popular analytical statistical software that include macros for carrying out meta-analysis. Himmelfarb has SPSS on some 3rd floor computers, and GW affiliates may download SAS to your own laptop from the Division of IT website. To perform mathematical analysis of big data sets there are statistical analysis software libraries in the R programming language available through GitHub and RStudio, but this requires advanced knowledge of the R and Python computer languages and data wrangling/cleaning.
  • PRISMA 2020 flow diagram generator The PRISMA Statement website has a page listing example flow diagram templates and a link to software for creating PRISMA 2020 flow diagrams using R software.

GW researchers may want to consider using Refworks to manage citations, and GW Box to store the full text PDF's of review articles. You can also use online survey forms such as Qualtrics, RedCAP, or Survey Monkey, to design and create your own coded fillable forms, and export the data to Excel or one of the qualitative analytical software tools listed above.

Forest Plot Generators

  • RevMan 5 the desktop version of the software used by Cochrane systematic review teams. RevMan 5 is free for academic use and can be downloaded and configured to run as stand alone software that does not connect with the Cochrane server if you follow the instructions at https://training.cochrane.org/online-learning/core-software-cochrane-reviews/revman/revman-5-download/non-cochrane-reviews.
  • Meta-Essentials a free set of workbooks designed for Microsoft Excel that, based on your input, automatically produce meta-analyses including Forest Plots. Produced for Erasmus University Rotterdam joint research institute.
  • Neyeloff, Fuchs & Moreira Another set of Excel worksheets and instructions to generate a Forest Plot. Published as Neyeloff, J.L., Fuchs, S.C. & Moreira, L.B. Meta-analyses and Forest plots using a microsoft excel spreadsheet: step-by-step guide focusing on descriptive data analysis. BMC Res Notes 5, 52 (2012). https://doi-org.proxygw.wrlc.org/10.1186/1756-0500-5-52
  • For R programmers instructions are at https://cran.r-project.org/web/packages/forestplot/vignettes/forestplot.html and you can download the R code package from https://github.com/gforge/forestplot
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A literature review is a discussion of the literature (aka. the "research" or "scholarship") surrounding a certain topic. A good literature review doesn't simply summarize the existing material, but provides thoughtful synthesis and analysis. The purpose of a literature review is to orient your own work within an existing body of knowledge. A literature review may be written as a standalone piece or be included in a larger body of work.

You can read more about literature reviews, what they entail, and how to write one, using the resources below. 

SAGE Research Methods Videos

Am i the only one struggling to write a literature review.

Dr. Zina O'Leary explains the misconceptions and struggles students often have with writing a literature review. She also provides step-by-step guidance on writing a persuasive literature review.

An Introduction to Literature Reviews

Dr. Eric Jensen, Professor of Sociology at the University of Warwick, and Dr. Charles Laurie, Director of Research at Verisk Maplecroft, explain how to write a literature review, and why researchers need to do so. Literature reviews can be stand-alone research or part of a larger project. They communicate the state of academic knowledge on a given topic, specifically detailing what is still unknown.

This is the first video in a whole series about literature reviews. You can find the rest of the series in our SAGE database, Research Methods:

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Videos covering research methods and statistics

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  • Literature Review This chapter in SAGE's Encyclopedia of Research Design describes the types of literature reviews and scientific standards for conducting literature reviews.
  • UNC Writing Center: Literature Reviews This handout from the Writing Center at UNC will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.
  • Purdue OWL: Writing a Literature Review The overview of literature reviews comes from Purdue's Online Writing Lab. It explains the basic why, what, and how of writing a literature review.

Organizational Tools for Literature Reviews

One of the most daunting aspects of writing a literature review is organizing your research. There are a variety of strategies that you can use to help you in this task. We've highlighted just a few ways writers keep track of all that information! You can use a combination of these tools or come up with your own organizational process. The key is choosing something that works with your own learning style.

Citation Managers

Citation managers are great tools, in general, for organizing research, but can be especially helpful when writing a literature review. You can keep all of your research in one place, take notes, and organize your materials into different folders or categories. Read more about citations managers here:

  • Manage Citations & Sources

Concept Mapping

Some writers use concept mapping (sometimes called flow or bubble charts or "mind maps") to help them visualize the ways in which the research they found connects.

methods for a literature review

There is no right or wrong way to make a concept map. There are a variety of online tools that can help you create a concept map or you can simply put pen to paper. To read more about concept mapping, take a look at the following help guides:

  • Using Concept Maps From Williams College's guide, Literature Review: A Self-guided Tutorial

Synthesis Matrix

A synthesis matrix is is a chart you can use to help you organize your research into thematic categories. By organizing your research into a matrix, like the examples below, can help you visualize the ways in which your sources connect. 

  • Walden University Writing Center: Literature Review Matrix Find a variety of literature review matrix examples and templates from Walden University.
  • Writing A Literature Review and Using a Synthesis Matrix An example synthesis matrix created by NC State University Writing and Speaking Tutorial Service Tutors. If you would like a copy of this synthesis matrix in a different format, like a Word document, please ask a librarian. CC-BY-SA 3.0
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What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position yourself in relation to other researchers and theorists
  • Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

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To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

  • Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
  • Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
  • Critically evaluate: mention the strengths and weaknesses of your sources.
  • Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarise yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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Conducting a Literature Review

  • Introduction

What is a Literature Review?

Goals of the literature review, types of liteature reviews, recommended reading.

  • Planning Your Literature Review
  • Choose Keywords
  • Decide where to search
  • Formulate Your Search Strategy
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  • When to Stop Searching
  • Using Ai for Searching the Literature
  • Evaluate, Synthesize & Analyze the Literature
  • Write a Literature Review

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A literature review surveys, summarizes, critically analyzes, compares, and synthesizes multiple scholarly works, or published knowledge on a particular topic or specific subject area.

Literature can include peer-reviewed or scholarly  articles, books/ ebooks, conference proceedings, theses/ dissertations, documents published by governmental agencies and non-profit organizations, and other forms of gray literature.

Conducting a literature review is part of the research process and serves to establish a base of knowledge and overview of the principal works on a specific area of research as well as identify important themes, discoveries, areas of consensus and debate, changes over time, and provide a foundation for further research.

A literature review may be written to:

  •     Synthesize past and current literature on a topic
  •     Identify a problem in a field of research  
  •     Show how the literature relates to one another
  •     Place your work in the the context of other related research

What kinds of sources require a Literature Review?

  •     A thesis or dissertation
  •     A grant proposal
  •     A research paper assigned in a course 
  •     An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

The following are common types of literature reviews:

Narrative or Traditional Review

The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

Systematic Review

The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find.

Meta-analysis

This type of review utilizes quantitative methods to combine the results of independent studies and synthesize summaries and conclusions which can be used to evaluate therapeutic effectiveness, plan new studies, etc.

Meta-synthesis

A meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic.

Further Reading on Different Types of Literature Reviews

Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies . Health Information and Libraries Journal, 26(2), 91-108. doi:10.1111/j.1471-1842.2009.00848.x Gough, D., Thomas, J., & Oliver, S. (2012). Clarifying differences between review designs and methods . Systematic Reviews, 1, 28. doi:10.1186/2046-4053-1-28

The library has a number of books on conducting and writing literature reviews. The following are some recommended ebooks available in the library:

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Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91–108. doi:10.1111/j.1471-1842.2009.00848.x

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An overview of methodological approaches in systematic reviews

Prabhakar veginadu.

1 Department of Rural Clinical Sciences, La Trobe Rural Health School, La Trobe University, Bendigo Victoria, Australia

Hanny Calache

2 Lincoln International Institute for Rural Health, University of Lincoln, Brayford Pool, Lincoln UK

Akshaya Pandian

3 Department of Orthodontics, Saveetha Dental College, Chennai Tamil Nadu, India

Mohd Masood

Associated data.

APPENDIX B: List of excluded studies with detailed reasons for exclusion

APPENDIX C: Quality assessment of included reviews using AMSTAR 2

The aim of this overview is to identify and collate evidence from existing published systematic review (SR) articles evaluating various methodological approaches used at each stage of an SR.

The search was conducted in five electronic databases from inception to November 2020 and updated in February 2022: MEDLINE, Embase, Web of Science Core Collection, Cochrane Database of Systematic Reviews, and APA PsycINFO. Title and abstract screening were performed in two stages by one reviewer, supported by a second reviewer. Full‐text screening, data extraction, and quality appraisal were performed by two reviewers independently. The quality of the included SRs was assessed using the AMSTAR 2 checklist.

The search retrieved 41,556 unique citations, of which 9 SRs were deemed eligible for inclusion in final synthesis. Included SRs evaluated 24 unique methodological approaches used for defining the review scope and eligibility, literature search, screening, data extraction, and quality appraisal in the SR process. Limited evidence supports the following (a) searching multiple resources (electronic databases, handsearching, and reference lists) to identify relevant literature; (b) excluding non‐English, gray, and unpublished literature, and (c) use of text‐mining approaches during title and abstract screening.

The overview identified limited SR‐level evidence on various methodological approaches currently employed during five of the seven fundamental steps in the SR process, as well as some methodological modifications currently used in expedited SRs. Overall, findings of this overview highlight the dearth of published SRs focused on SR methodologies and this warrants future work in this area.

1. INTRODUCTION

Evidence synthesis is a prerequisite for knowledge translation. 1 A well conducted systematic review (SR), often in conjunction with meta‐analyses (MA) when appropriate, is considered the “gold standard” of methods for synthesizing evidence related to a topic of interest. 2 The central strength of an SR is the transparency of the methods used to systematically search, appraise, and synthesize the available evidence. 3 Several guidelines, developed by various organizations, are available for the conduct of an SR; 4 , 5 , 6 , 7 among these, Cochrane is considered a pioneer in developing rigorous and highly structured methodology for the conduct of SRs. 8 The guidelines developed by these organizations outline seven fundamental steps required in SR process: defining the scope of the review and eligibility criteria, literature searching and retrieval, selecting eligible studies, extracting relevant data, assessing risk of bias (RoB) in included studies, synthesizing results, and assessing certainty of evidence (CoE) and presenting findings. 4 , 5 , 6 , 7

The methodological rigor involved in an SR can require a significant amount of time and resource, which may not always be available. 9 As a result, there has been a proliferation of modifications made to the traditional SR process, such as refining, shortening, bypassing, or omitting one or more steps, 10 , 11 for example, limits on the number and type of databases searched, limits on publication date, language, and types of studies included, and limiting to one reviewer for screening and selection of studies, as opposed to two or more reviewers. 10 , 11 These methodological modifications are made to accommodate the needs of and resource constraints of the reviewers and stakeholders (e.g., organizations, policymakers, health care professionals, and other knowledge users). While such modifications are considered time and resource efficient, they may introduce bias in the review process reducing their usefulness. 5

Substantial research has been conducted examining various approaches used in the standardized SR methodology and their impact on the validity of SR results. There are a number of published reviews examining the approaches or modifications corresponding to single 12 , 13 or multiple steps 14 involved in an SR. However, there is yet to be a comprehensive summary of the SR‐level evidence for all the seven fundamental steps in an SR. Such a holistic evidence synthesis will provide an empirical basis to confirm the validity of current accepted practices in the conduct of SRs. Furthermore, sometimes there is a balance that needs to be achieved between the resource availability and the need to synthesize the evidence in the best way possible, given the constraints. This evidence base will also inform the choice of modifications to be made to the SR methods, as well as the potential impact of these modifications on the SR results. An overview is considered the choice of approach for summarizing existing evidence on a broad topic, directing the reader to evidence, or highlighting the gaps in evidence, where the evidence is derived exclusively from SRs. 15 Therefore, for this review, an overview approach was used to (a) identify and collate evidence from existing published SR articles evaluating various methodological approaches employed in each of the seven fundamental steps of an SR and (b) highlight both the gaps in the current research and the potential areas for future research on the methods employed in SRs.

An a priori protocol was developed for this overview but was not registered with the International Prospective Register of Systematic Reviews (PROSPERO), as the review was primarily methodological in nature and did not meet PROSPERO eligibility criteria for registration. The protocol is available from the corresponding author upon reasonable request. This overview was conducted based on the guidelines for the conduct of overviews as outlined in The Cochrane Handbook. 15 Reporting followed the Preferred Reporting Items for Systematic reviews and Meta‐analyses (PRISMA) statement. 3

2.1. Eligibility criteria

Only published SRs, with or without associated MA, were included in this overview. We adopted the defining characteristics of SRs from The Cochrane Handbook. 5 According to The Cochrane Handbook, a review was considered systematic if it satisfied the following criteria: (a) clearly states the objectives and eligibility criteria for study inclusion; (b) provides reproducible methodology; (c) includes a systematic search to identify all eligible studies; (d) reports assessment of validity of findings of included studies (e.g., RoB assessment of the included studies); (e) systematically presents all the characteristics or findings of the included studies. 5 Reviews that did not meet all of the above criteria were not considered a SR for this study and were excluded. MA‐only articles were included if it was mentioned that the MA was based on an SR.

SRs and/or MA of primary studies evaluating methodological approaches used in defining review scope and study eligibility, literature search, study selection, data extraction, RoB assessment, data synthesis, and CoE assessment and reporting were included. The methodological approaches examined in these SRs and/or MA can also be related to the substeps or elements of these steps; for example, applying limits on date or type of publication are the elements of literature search. Included SRs examined or compared various aspects of a method or methods, and the associated factors, including but not limited to: precision or effectiveness; accuracy or reliability; impact on the SR and/or MA results; reproducibility of an SR steps or bias occurred; time and/or resource efficiency. SRs assessing the methodological quality of SRs (e.g., adherence to reporting guidelines), evaluating techniques for building search strategies or the use of specific database filters (e.g., use of Boolean operators or search filters for randomized controlled trials), examining various tools used for RoB or CoE assessment (e.g., ROBINS vs. Cochrane RoB tool), or evaluating statistical techniques used in meta‐analyses were excluded. 14

2.2. Search

The search for published SRs was performed on the following scientific databases initially from inception to third week of November 2020 and updated in the last week of February 2022: MEDLINE (via Ovid), Embase (via Ovid), Web of Science Core Collection, Cochrane Database of Systematic Reviews, and American Psychological Association (APA) PsycINFO. Search was restricted to English language publications. Following the objectives of this study, study design filters within databases were used to restrict the search to SRs and MA, where available. The reference lists of included SRs were also searched for potentially relevant publications.

The search terms included keywords, truncations, and subject headings for the key concepts in the review question: SRs and/or MA, methods, and evaluation. Some of the terms were adopted from the search strategy used in a previous review by Robson et al., which reviewed primary studies on methodological approaches used in study selection, data extraction, and quality appraisal steps of SR process. 14 Individual search strategies were developed for respective databases by combining the search terms using appropriate proximity and Boolean operators, along with the related subject headings in order to identify SRs and/or MA. 16 , 17 A senior librarian was consulted in the design of the search terms and strategy. Appendix A presents the detailed search strategies for all five databases.

2.3. Study selection and data extraction

Title and abstract screening of references were performed in three steps. First, one reviewer (PV) screened all the titles and excluded obviously irrelevant citations, for example, articles on topics not related to SRs, non‐SR publications (such as randomized controlled trials, observational studies, scoping reviews, etc.). Next, from the remaining citations, a random sample of 200 titles and abstracts were screened against the predefined eligibility criteria by two reviewers (PV and MM), independently, in duplicate. Discrepancies were discussed and resolved by consensus. This step ensured that the responses of the two reviewers were calibrated for consistency in the application of the eligibility criteria in the screening process. Finally, all the remaining titles and abstracts were reviewed by a single “calibrated” reviewer (PV) to identify potential full‐text records. Full‐text screening was performed by at least two authors independently (PV screened all the records, and duplicate assessment was conducted by MM, HC, or MG), with discrepancies resolved via discussions or by consulting a third reviewer.

Data related to review characteristics, results, key findings, and conclusions were extracted by at least two reviewers independently (PV performed data extraction for all the reviews and duplicate extraction was performed by AP, HC, or MG).

2.4. Quality assessment of included reviews

The quality assessment of the included SRs was performed using the AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews). The tool consists of a 16‐item checklist addressing critical and noncritical domains. 18 For the purpose of this study, the domain related to MA was reclassified from critical to noncritical, as SRs with and without MA were included. The other six critical domains were used according to the tool guidelines. 18 Two reviewers (PV and AP) independently responded to each of the 16 items in the checklist with either “yes,” “partial yes,” or “no.” Based on the interpretations of the critical and noncritical domains, the overall quality of the review was rated as high, moderate, low, or critically low. 18 Disagreements were resolved through discussion or by consulting a third reviewer.

2.5. Data synthesis

To provide an understandable summary of existing evidence syntheses, characteristics of the methods evaluated in the included SRs were examined and key findings were categorized and presented based on the corresponding step in the SR process. The categories of key elements within each step were discussed and agreed by the authors. Results of the included reviews were tabulated and summarized descriptively, along with a discussion on any overlap in the primary studies. 15 No quantitative analyses of the data were performed.

From 41,556 unique citations identified through literature search, 50 full‐text records were reviewed, and nine systematic reviews 14 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 were deemed eligible for inclusion. The flow of studies through the screening process is presented in Figure  1 . A list of excluded studies with reasons can be found in Appendix B .

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Study selection flowchart

3.1. Characteristics of included reviews

Table  1 summarizes the characteristics of included SRs. The majority of the included reviews (six of nine) were published after 2010. 14 , 22 , 23 , 24 , 25 , 26 Four of the nine included SRs were Cochrane reviews. 20 , 21 , 22 , 23 The number of databases searched in the reviews ranged from 2 to 14, 2 reviews searched gray literature sources, 24 , 25 and 7 reviews included a supplementary search strategy to identify relevant literature. 14 , 19 , 20 , 21 , 22 , 23 , 26 Three of the included SRs (all Cochrane reviews) included an integrated MA. 20 , 21 , 23

Characteristics of included studies

SR = systematic review; MA = meta‐analysis; RCT = randomized controlled trial; CCT = controlled clinical trial; N/R = not reported.

The included SRs evaluated 24 unique methodological approaches (26 in total) used across five steps in the SR process; 8 SRs evaluated 6 approaches, 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 while 1 review evaluated 18 approaches. 14 Exclusion of gray or unpublished literature 21 , 26 and blinding of reviewers for RoB assessment 14 , 23 were evaluated in two reviews each. Included SRs evaluated methods used in five different steps in the SR process, including methods used in defining the scope of review ( n  = 3), literature search ( n  = 3), study selection ( n  = 2), data extraction ( n  = 1), and RoB assessment ( n  = 2) (Table  2 ).

Summary of findings from review evaluating systematic review methods

There was some overlap in the primary studies evaluated in the included SRs on the same topics: Schmucker et al. 26 and Hopewell et al. 21 ( n  = 4), Hopewell et al. 20 and Crumley et al. 19 ( n  = 30), and Robson et al. 14 and Morissette et al. 23 ( n  = 4). There were no conflicting results between any of the identified SRs on the same topic.

3.2. Methodological quality of included reviews

Overall, the quality of the included reviews was assessed as moderate at best (Table  2 ). The most common critical weakness in the reviews was failure to provide justification for excluding individual studies (four reviews). Detailed quality assessment is provided in Appendix C .

3.3. Evidence on systematic review methods

3.3.1. methods for defining review scope and eligibility.

Two SRs investigated the effect of excluding data obtained from gray or unpublished sources on the pooled effect estimates of MA. 21 , 26 Hopewell et al. 21 reviewed five studies that compared the impact of gray literature on the results of a cohort of MA of RCTs in health care interventions. Gray literature was defined as information published in “print or electronic sources not controlled by commercial or academic publishers.” Findings showed an overall greater treatment effect for published trials than trials reported in gray literature. In a more recent review, Schmucker et al. 26 addressed similar objectives, by investigating gray and unpublished data in medicine. In addition to gray literature, defined similar to the previous review by Hopewell et al., the authors also evaluated unpublished data—defined as “supplemental unpublished data related to published trials, data obtained from the Food and Drug Administration  or other regulatory websites or postmarketing analyses hidden from the public.” The review found that in majority of the MA, excluding gray literature had little or no effect on the pooled effect estimates. The evidence was limited to conclude if the data from gray and unpublished literature had an impact on the conclusions of MA. 26

Morrison et al. 24 examined five studies measuring the effect of excluding non‐English language RCTs on the summary treatment effects of SR‐based MA in various fields of conventional medicine. Although none of the included studies reported major difference in the treatment effect estimates between English only and non‐English inclusive MA, the review found inconsistent evidence regarding the methodological and reporting quality of English and non‐English trials. 24 As such, there might be a risk of introducing “language bias” when excluding non‐English language RCTs. The authors also noted that the numbers of non‐English trials vary across medical specialties, as does the impact of these trials on MA results. Based on these findings, Morrison et al. 24 conclude that literature searches must include non‐English studies when resources and time are available to minimize the risk of introducing “language bias.”

3.3.2. Methods for searching studies

Crumley et al. 19 analyzed recall (also referred to as “sensitivity” by some researchers; defined as “percentage of relevant studies identified by the search”) and precision (defined as “percentage of studies identified by the search that were relevant”) when searching a single resource to identify randomized controlled trials and controlled clinical trials, as opposed to searching multiple resources. The studies included in their review frequently compared a MEDLINE only search with the search involving a combination of other resources. The review found low median recall estimates (median values between 24% and 92%) and very low median precisions (median values between 0% and 49%) for most of the electronic databases when searched singularly. 19 A between‐database comparison, based on the type of search strategy used, showed better recall and precision for complex and Cochrane Highly Sensitive search strategies (CHSSS). In conclusion, the authors emphasize that literature searches for trials in SRs must include multiple sources. 19

In an SR comparing handsearching and electronic database searching, Hopewell et al. 20 found that handsearching retrieved more relevant RCTs (retrieval rate of 92%−100%) than searching in a single electronic database (retrieval rates of 67% for PsycINFO/PsycLIT, 55% for MEDLINE, and 49% for Embase). The retrieval rates varied depending on the quality of handsearching, type of electronic search strategy used (e.g., simple, complex or CHSSS), and type of trial reports searched (e.g., full reports, conference abstracts, etc.). The authors concluded that handsearching was particularly important in identifying full trials published in nonindexed journals and in languages other than English, as well as those published as abstracts and letters. 20

The effectiveness of checking reference lists to retrieve additional relevant studies for an SR was investigated by Horsley et al. 22 The review reported that checking reference lists yielded 2.5%–40% more studies depending on the quality and comprehensiveness of the electronic search used. The authors conclude that there is some evidence, although from poor quality studies, to support use of checking reference lists to supplement database searching. 22

3.3.3. Methods for selecting studies

Three approaches relevant to reviewer characteristics, including number, experience, and blinding of reviewers involved in the screening process were highlighted in an SR by Robson et al. 14 Based on the retrieved evidence, the authors recommended that two independent, experienced, and unblinded reviewers be involved in study selection. 14 A modified approach has also been suggested by the review authors, where one reviewer screens and the other reviewer verifies the list of excluded studies, when the resources are limited. It should be noted however this suggestion is likely based on the authors’ opinion, as there was no evidence related to this from the studies included in the review.

Robson et al. 14 also reported two methods describing the use of technology for screening studies: use of Google Translate for translating languages (for example, German language articles to English) to facilitate screening was considered a viable method, while using two computer monitors for screening did not increase the screening efficiency in SR. Title‐first screening was found to be more efficient than simultaneous screening of titles and abstracts, although the gain in time with the former method was lesser than the latter. Therefore, considering that the search results are routinely exported as titles and abstracts, Robson et al. 14 recommend screening titles and abstracts simultaneously. However, the authors note that these conclusions were based on very limited number (in most instances one study per method) of low‐quality studies. 14

3.3.4. Methods for data extraction

Robson et al. 14 examined three approaches for data extraction relevant to reviewer characteristics, including number, experience, and blinding of reviewers (similar to the study selection step). Although based on limited evidence from a small number of studies, the authors recommended use of two experienced and unblinded reviewers for data extraction. The experience of the reviewers was suggested to be especially important when extracting continuous outcomes (or quantitative) data. However, when the resources are limited, data extraction by one reviewer and a verification of the outcomes data by a second reviewer was recommended.

As for the methods involving use of technology, Robson et al. 14 identified limited evidence on the use of two monitors to improve the data extraction efficiency and computer‐assisted programs for graphical data extraction. However, use of Google Translate for data extraction in non‐English articles was not considered to be viable. 14 In the same review, Robson et al. 14 identified evidence supporting contacting authors for obtaining additional relevant data.

3.3.5. Methods for RoB assessment

Two SRs examined the impact of blinding of reviewers for RoB assessments. 14 , 23 Morissette et al. 23 investigated the mean differences between the blinded and unblinded RoB assessment scores and found inconsistent differences among the included studies providing no definitive conclusions. Similar conclusions were drawn in a more recent review by Robson et al., 14 which included four studies on reviewer blinding for RoB assessment that completely overlapped with Morissette et al. 23

Use of experienced reviewers and provision of additional guidance for RoB assessment were examined by Robson et al. 14 The review concluded that providing intensive training and guidance on assessing studies reporting insufficient data to the reviewers improves RoB assessments. 14 Obtaining additional data related to quality assessment by contacting study authors was also found to help the RoB assessments, although based on limited evidence. When assessing the qualitative or mixed method reviews, Robson et al. 14 recommends the use of a structured RoB tool as opposed to an unstructured tool. No SRs were identified on data synthesis and CoE assessment and reporting steps.

4. DISCUSSION

4.1. summary of findings.

Nine SRs examining 24 unique methods used across five steps in the SR process were identified in this overview. The collective evidence supports some current traditional and modified SR practices, while challenging other approaches. However, the quality of the included reviews was assessed to be moderate at best and in the majority of the included SRs, evidence related to the evaluated methods was obtained from very limited numbers of primary studies. As such, the interpretations from these SRs should be made cautiously.

The evidence gathered from the included SRs corroborate a few current SR approaches. 5 For example, it is important to search multiple resources for identifying relevant trials (RCTs and/or CCTs). The resources must include a combination of electronic database searching, handsearching, and reference lists of retrieved articles. 5 However, no SRs have been identified that evaluated the impact of the number of electronic databases searched. A recent study by Halladay et al. 27 found that articles on therapeutic intervention, retrieved by searching databases other than PubMed (including Embase), contributed only a small amount of information to the MA and also had a minimal impact on the MA results. The authors concluded that when the resources are limited and when large number of studies are expected to be retrieved for the SR or MA, PubMed‐only search can yield reliable results. 27

Findings from the included SRs also reiterate some methodological modifications currently employed to “expedite” the SR process. 10 , 11 For example, excluding non‐English language trials and gray/unpublished trials from MA have been shown to have minimal or no impact on the results of MA. 24 , 26 However, the efficiency of these SR methods, in terms of time and the resources used, have not been evaluated in the included SRs. 24 , 26 Of the SRs included, only two have focused on the aspect of efficiency 14 , 25 ; O'Mara‐Eves et al. 25 report some evidence to support the use of text‐mining approaches for title and abstract screening in order to increase the rate of screening. Moreover, only one included SR 14 considered primary studies that evaluated reliability (inter‐ or intra‐reviewer consistency) and accuracy (validity when compared against a “gold standard” method) of the SR methods. This can be attributed to the limited number of primary studies that evaluated these outcomes when evaluating the SR methods. 14 Lack of outcome measures related to reliability, accuracy, and efficiency precludes making definitive recommendations on the use of these methods/modifications. Future research studies must focus on these outcomes.

Some evaluated methods may be relevant to multiple steps; for example, exclusions based on publication status (gray/unpublished literature) and language of publication (non‐English language studies) can be outlined in the a priori eligibility criteria or can be incorporated as search limits in the search strategy. SRs included in this overview focused on the effect of study exclusions on pooled treatment effect estimates or MA conclusions. Excluding studies from the search results, after conducting a comprehensive search, based on different eligibility criteria may yield different results when compared to the results obtained when limiting the search itself. 28 Further studies are required to examine this aspect.

Although we acknowledge the lack of standardized quality assessment tools for methodological study designs, we adhered to the Cochrane criteria for identifying SRs in this overview. This was done to ensure consistency in the quality of the included evidence. As a result, we excluded three reviews that did not provide any form of discussion on the quality of the included studies. The methods investigated in these reviews concern supplementary search, 29 data extraction, 12 and screening. 13 However, methods reported in two of these three reviews, by Mathes et al. 12 and Waffenschmidt et al., 13 have also been examined in the SR by Robson et al., 14 which was included in this overview; in most instances (with the exception of one study included in Mathes et al. 12 and Waffenschmidt et al. 13 each), the studies examined in these excluded reviews overlapped with those in the SR by Robson et al. 14

One of the key gaps in the knowledge observed in this overview was the dearth of SRs on the methods used in the data synthesis component of SR. Narrative and quantitative syntheses are the two most commonly used approaches for synthesizing data in evidence synthesis. 5 There are some published studies on the proposed indications and implications of these two approaches. 30 , 31 These studies found that both data synthesis methods produced comparable results and have their own advantages, suggesting that the choice of the method must be based on the purpose of the review. 31 With increasing number of “expedited” SR approaches (so called “rapid reviews”) avoiding MA, 10 , 11 further research studies are warranted in this area to determine the impact of the type of data synthesis on the results of the SR.

4.2. Implications for future research

The findings of this overview highlight several areas of paucity in primary research and evidence synthesis on SR methods. First, no SRs were identified on methods used in two important components of the SR process, including data synthesis and CoE and reporting. As for the included SRs, a limited number of evaluation studies have been identified for several methods. This indicates that further research is required to corroborate many of the methods recommended in current SR guidelines. 4 , 5 , 6 , 7 Second, some SRs evaluated the impact of methods on the results of quantitative synthesis and MA conclusions. Future research studies must also focus on the interpretations of SR results. 28 , 32 Finally, most of the included SRs were conducted on specific topics related to the field of health care, limiting the generalizability of the findings to other areas. It is important that future research studies evaluating evidence syntheses broaden the objectives and include studies on different topics within the field of health care.

4.3. Strengths and limitations

To our knowledge, this is the first overview summarizing current evidence from SRs and MA on different methodological approaches used in several fundamental steps in SR conduct. The overview methodology followed well established guidelines and strict criteria defined for the inclusion of SRs.

There are several limitations related to the nature of the included reviews. Evidence for most of the methods investigated in the included reviews was derived from a limited number of primary studies. Also, the majority of the included SRs may be considered outdated as they were published (or last updated) more than 5 years ago 33 ; only three of the nine SRs have been published in the last 5 years. 14 , 25 , 26 Therefore, important and recent evidence related to these topics may not have been included. Substantial numbers of included SRs were conducted in the field of health, which may limit the generalizability of the findings. Some method evaluations in the included SRs focused on quantitative analyses components and MA conclusions only. As such, the applicability of these findings to SR more broadly is still unclear. 28 Considering the methodological nature of our overview, limiting the inclusion of SRs according to the Cochrane criteria might have resulted in missing some relevant evidence from those reviews without a quality assessment component. 12 , 13 , 29 Although the included SRs performed some form of quality appraisal of the included studies, most of them did not use a standardized RoB tool, which may impact the confidence in their conclusions. Due to the type of outcome measures used for the method evaluations in the primary studies and the included SRs, some of the identified methods have not been validated against a reference standard.

Some limitations in the overview process must be noted. While our literature search was exhaustive covering five bibliographic databases and supplementary search of reference lists, no gray sources or other evidence resources were searched. Also, the search was primarily conducted in health databases, which might have resulted in missing SRs published in other fields. Moreover, only English language SRs were included for feasibility. As the literature search retrieved large number of citations (i.e., 41,556), the title and abstract screening was performed by a single reviewer, calibrated for consistency in the screening process by another reviewer, owing to time and resource limitations. These might have potentially resulted in some errors when retrieving and selecting relevant SRs. The SR methods were grouped based on key elements of each recommended SR step, as agreed by the authors. This categorization pertains to the identified set of methods and should be considered subjective.

5. CONCLUSIONS

This overview identified limited SR‐level evidence on various methodological approaches currently employed during five of the seven fundamental steps in the SR process. Limited evidence was also identified on some methodological modifications currently used to expedite the SR process. Overall, findings highlight the dearth of SRs on SR methodologies, warranting further work to confirm several current recommendations on conventional and expedited SR processes.

CONFLICT OF INTEREST

The authors declare no conflicts of interest.

Supporting information

APPENDIX A: Detailed search strategies

ACKNOWLEDGMENTS

The first author is supported by a La Trobe University Full Fee Research Scholarship and a Graduate Research Scholarship.

Open Access Funding provided by La Trobe University.

Veginadu P, Calache H, Gussy M, Pandian A, Masood M. An overview of methodological approaches in systematic reviews . J Evid Based Med . 2022; 15 :39–54. 10.1111/jebm.12468 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

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How to write the methods section of a systematic review

Home | Blog | How To | How to write the methods section of a systematic review

Covidence breaks down how to write a methods section

The methods section of your systematic review describes what you did, how you did it, and why. Readers need this information to interpret the results and conclusions of the review. Often, a lot of information needs to be distilled into just a few paragraphs. This can be a challenging task, but good preparation and the right tools will help you to set off in the right direction 🗺️🧭.

Systematic reviews are so-called because they are conducted in a way that is rigorous and replicable. So it’s important that these methods are reported in a way that is thorough, clear, and easy to navigate for the reader – whether that’s a patient, a healthcare worker, or a researcher. 

Like most things in a systematic review, the methods should be planned upfront and ideally described in detail in a project plan or protocol. Reviews of healthcare interventions follow the PRISMA guidelines for the minimum set of items to report in the methods section. But what else should be included? It’s a good idea to consider what readers will want to know about the review methods and whether the journal you’re planning to submit the work to has expectations on the reporting of methods. Finding out in advance will help you to plan what to include.

methods for a literature review

Describe what happened

While the research plan sets out what you intend to do, the methods section is a write-up of what actually happened. It’s not a simple case of rewriting the plan in the past tense – you will also need to discuss and justify deviations from the plan and describe the handling of issues that were unforeseen at the time the plan was written. For this reason, it is useful to make detailed notes before, during, and after the review is completed. Relying on memory alone risks losing valuable information and trawling through emails when the deadline is looming can be frustrating and time consuming! 

Keep it brief

The methods section should be succinct but include all the noteworthy information. This can be a difficult balance to achieve. A useful strategy is to aim for a brief description that signposts the reader to a separate section or sections of supporting information. This could include datasets, a flowchart to show what happened to the excluded studies, a collection of search strategies, and tables containing detailed information about the studies.This separation keeps the review short and simple while enabling the reader to drill down to the detail as needed. And if the methods follow a well-known or standard process, it might suffice to say so and give a reference, rather than describe the process at length. 

Follow a structure

A clear structure provides focus. Use of descriptive headings keeps the writing on track and helps the reader get to key information quickly. What should the structure of the methods section look like? As always, a lot depends on the type of review but it will certainly contain information relating to the following areas:

  • Selection criteria ⭕
  • Data collection and analysis 👩‍💻
  • Study quality and risk of bias ⚖️

Let’s look at each of these in turn.

1. Selection criteria ⭕

The criteria for including and excluding studies are listed here. This includes detail about the types of studies, the types of participants, the types of interventions and the types of outcomes and how they were measured. 

2. Search 🕵🏾‍♀️

Comprehensive reporting of the search is important because this means it can be evaluated and replicated. The search strategies are included in the review, along with details of the databases searched. It’s also important to list any restrictions on the search (for example, language), describe how resources other than electronic databases were searched (for example,  non-indexed journals), and give the date that the searches were run. The PRISMA-S extension provides guidance on reporting literature searches. 

methods for a literature review

Systematic reviewer pro-tip:

 Copy and paste the search strategy to avoid introducing typos

3. Data collection and analysis 👩‍💻

This section describes:

  • how studies were selected for inclusion in the review
  • how study data were extracted from the study reports
  • how study data were combined for analysis and synthesis

To describe how studies were selected for inclusion , review teams outline the screening process. Covidence uses reviewers’ decision data to automatically populate a PRISMA flow diagram for this purpose. Covidence can also calculate Cohen’s kappa to enable review teams to report the level of agreement among individual reviewers during screening.

To describe how study data were extracted from the study reports , reviewers outline the form that was used, any pilot-testing that was done, and the items that were extracted from the included studies. An important piece of information to include here is the process used to resolve conflict among the reviewers. Covidence’s data extraction tool saves reviewers’ comments and notes in the system as they work. This keeps the information in one place for easy retrieval ⚡.

To describe how study data were combined for analysis and synthesis, reviewers outline the type of synthesis (narrative or quantitative, for example), the methods for grouping data, the challenges that came up, and how these were dealt with. If the review includes a meta-analysis, it will detail how this was performed and how the treatment effects were measured.

4. Study quality and risk of bias ⚖️

Because the results of systematic reviews can be affected by many types of bias, reviewers make every effort to minimise it and to show the reader that the methods they used were appropriate. This section describes the methods used to assess study quality and an assessment of the risk of bias across a range of domains. 

Steps to assess the risk of bias in studies include looking at how study participants were assigned to treatment groups and whether patients and/or study assessors were blinded to the treatment given. Reviewers also report their assessment of the risk of bias due to missing outcome data, whether that is due to participant drop-out or non-reporting of the outcomes by the study authors.

Covidence’s default template for assessing study quality is Cochrane’s risk of bias tool but it is also possible to start from scratch and build a tool with a set of custom domains if you prefer.

Careful planning, clear writing, and a structured approach are key to a good methods section. A methodologist will be able to refer review teams to examples of good methods reporting in the literature. Covidence helps reviewers to screen references, extract data and complete risk of bias tables quickly and efficiently. Sign up for a free trial today!

Laura Mellor. Portsmouth, UK

Laura Mellor. Portsmouth, UK

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SYSTEMATIC REVIEW article

A systematic literature review on the utilization of extended operating room hours to reduce surgical backlogs.

\nMariana Oliveira

  • 1 CEGIST, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
  • 2 Department of Logistics and Operations Management, HEC Montreal, Montreal, QC, Canada
  • 3 Interuniversity Research Centre on Enterprise Networks, Logistics and Transportation (CIRRELT), Quebec City, QC, Canada
  • 4 Faculty of Business Administration, Université Laval, Quebec City, QC, Canada

This article is part of the Research Topic ‘ Health Systems Recovery in the Context of COVID-19 and Protracted Conflict '

Introduction: Hospital managers address elective patient surgical backlogs with different strategies: increasing installed capacity, managing demand and improving efficiency. Recently, and particularly since the COVID-19 elective surgery suspension, extended operating room hours has been used to reduce waiting lists by taking advantage of empty operating rooms and existing surgical teams.

Methods: Two research questions are raised: (1) which are the scientific literature's insights related to the use of extended operating room hours to help reduce surgery backlogs? and (2) provided that a hospital decides to extend its operating room opening time, what are the main challenges and the key aspects to consider in the design and implementation of policies to manage extended operating room hours? A systematic review on Web of Science database was conducted to gather existing literature, published from January 2012 to December 2021, regarding strategies to reduce waiting lists using empty operating rooms outside regular working hours.

Results: A total of 12 papers were selected as relevant to address the two research questions. Results were organized according to their main features, namely setting, type of strategy, methodology, and how human resources are handled.

Discussion: The review suggests that extended operating room hours might be problematic if current staff is used and that a careful choice of patients should be made. However, its potential to reduce waiting times and its implications are discussed only superficially. Therefore, we analyze the implications of extending operating room hours from four different perspectives (management, staff, patients, and strategy deployment) and define some recommendations for policy makers and healthcare managers when implementing it in practice.

1. Introduction

Long waiting lists for surgical care are a significant problem with an impact on patient satisfaction and outcomes. In OECD countries, patients can wait up to several months to have their surgery performed ( 1 ). For instance, in Portugal, by the end of 2019, over 27,000 patients on waiting lists had been waiting for more than one year to receive surgery ( 2 ). The COVID-19 pandemic has drastically worsened the situation as most hospitals had to cancel or reduce elective surgeries. In the United States, Berlin et al. ( 3 ) report a decrease of around 35% in the number of surgeries performed between March and July 2020, when compared to the same period in 2019, and estimate that hospitals in the United States would need to work at 120% of their historical throughput during ten months to be able to work through two months of additional surgical demand in <1 year. Aldecoa et al. ( 4 ) estimate that the number of elective surgeries that were canceled or postponed worldwide during the 12-week period of disruption in spring 2020 amounts to 28,404,600. As a consequence, health organizations face considerable surgery backlogs. This is an issue that deserves attention due to their strong impact on the health system and the patients ( 5 ). In order to guarantee timely access to care, innovative and systematic approaches must be considered.

Broadly speaking, three approaches can be adopted to increase surgical activity: increase the installed capacity (infrastructure, human resources, and equipment), manage demand (for example, by offering alternative treatments), and improve efficiency. A straightforward manner to reduce waiting lists is by increasing capacity by constructing new operating rooms (OR) or training additional staff. However, this may take several years ( 6 ), thus, it is a strategy that can only be used as a long-term one. OR capacity can also be increased by improving practices, either through maximizing OR business hours utilization or minimizing idle times ( 7 – 9 ), or by reducing surgery lengths, for example, using more advanced procedures or more sophisticated equipment. Finally, financial incentives ( 1 ) have also led to increases in surgery productivity, although the reported improvements varied considerably between hospitals ( 10 ).

This paper is devoted to a fourth approach that differs in a subtle yet profound manner from the previous ones. The approach, which will be referred to as extended OR hours, has been observed in some hospitals and consists, essentially, of extending the use of OR beyond their regular opening hours to allow the existing surgical teams to increase their production. OR are usually open for a maximum of 10 h a day and, in most cases, are idle and not staffed for the remaining 14 h (except for emergency patients) ( 11 ). Additionally, given the availability of resources or due to cancellations or other unforeseen events, not all regular open hours of OR defined in the master surgery schedule (MSS) are effectively used for surgery. For instance, hospitals in Portugal and Spain receive an extra payment from their national healthcare systems for each surgery performed outside the regular working hours of OR ( 1 ). A part of this extra payment is then distributed among the members of the team performing the surgery. Indeed, extended OR hours increase the funding dedicated to surgical activities without increasing the installed capacity, since hospitals use the already available resources (OR and staff) to perform more surgeries. Extended OR hours should not be confused with classical extra-time management, which refers to cases where a surgery scheduled in regular time finishes later than the closing time of OR, either because it took longer than expected or because its starting time was delayed. Moreover, in extended OR hours, the surgical teams are not forced but rather invited to work additional hours on a voluntary basis, which means that hospitals need to negotiate and stimulate their participation.

Surprisingly, despite some basic administrative information concerning the funding procedures associated with the payment of the surgeries carried out outside regular hours of OR, we were not able to find rules or guidelines framing the use of extended OR hours with respect to how to decide the number, the time and the profile of the specific surgeries to perform in extended time. Furthermore, we did not find any document linking or coordinating the planning of surgeries to perform in extended OR hours to the master surgery schedule (MSS) plan that establishes the regular OR production. Considering the utter need for increasing the volume of surgeries, we believe that hospitals worldwide are, or will be soon, considering similar approaches to cope with such never seen before backlogs and, consequently, face the challenges and lack of guidelines to implement them.

Extended OR hours are a possible solution to these backlogs, given that they seek to achieve a temporary capacity increase by bringing into play existing staff and OR resources outside the regular working hours. In the short term, the benefits of performing surgeries in extended OR hours are straightforward: more surgeries, staff premiums, and higher hospital income. However, if the problem of elective surgical patient backlogs is structural, the rightness of extended OR hours production must be carefully assessed, since the implementation of such strategies requires the agreement of the OR staff and affects the rest of the human resources of the hospital and, clearly, the patients.

In fact, OR staff involvement is a necessary condition for extended OR hours to be used as a strategy. Lovejoy and Li ( 11 ) discussed hospital negotiations with surgical staff concerning evening work. Surgeons and staff avoid work during these hours because of two reasons: quality-of-life considerations and accumulated delays during the day. The authors conclude that mitigating the uncertainty at the beginning of the period from which the OR might be available for extended hours, alongside bonus payments, might reduce resistance to fill in OR extended hours. For this reason, we can conclude that the use of extended OR hours requires adequate planning.

The literature on OR planning is comprised of many studies focused on a large spectrum of decisions, such as the case-mix (i.e., the volume and properties of the surgical services to be offered by a hospital), the capacity to be installed in the hospital (namely how many OR and their staffing), the assignment of the available capacity to surgical specialties or groups of surgeons (also known as the master surgery schedule, MSS), the assignment of patients to specific OR sessions, and the scheduling of surgeries within sessions ( 12 ). However, these studies concern a regular activity context. Extended OR hours go beyond the standard OR planning and scheduling framework, raising specific questions and challenges, and it has not been, to the best of our knowledge, formalized and treated before in the literature.

At this point, it is important to reiterate that this concept should not be mistaken with related concepts such as flexible contracts, open scheduling, modified block scheduling, or overtime. Furthermore, as healthcare systems operate differently from one country to another, and due to the interdependence of the resources involved in OR planning, it is unrealistic to expect a single solution to explore extended OR hours that fit all the cases. Therefore, it is important to review and consider all the different perspectives and application contexts concerning the literature with respect to the use of extended OR hours before considering its deployment.

In this context, this paper raises the two following main research questions: (1) which are the scientific literature's insights related to the use of extended operating room hours to help reduce surgery backlogs?; and (2) provided that a hospital decides to extend its OR opening time, what are the main challenges and the key aspects to consider in the design and implementation of policies to manage extended OR hours? To answer, at least partially, these broad yet important questions, this paper develops a systematic review of the literature devoted to OR capacity planning with a focus on contexts where surgeries can be scheduled outside of the regular working hours. The works reported by the search will then be used to understand the implications of increasing OR hours as a strategy to reduce surgical backlogs. This analysis should raise discussions, both at the hospital and the national levels, on how to manage this potential avenue to expand surgical capacity. To the best of our knowledge, this is the first work that reviews the scientific literature on OR planning with the aim of formalizing the use of the idle OR capacity.

The remainder of this paper is structured as follows. Section 2 describes the methodology used to identify the scientific works related to extended OR hours, and Section 3 discusses the main findings of the literature review. Section 4 discusses important considerations regarding the management of extended OR hours and establishes the main practice implications of implementing such a strategy.

This section describes the methodology applied to search the scientific literature and to identify the contributions that include any strategy, model or case that aims to reduce surgical waiting lists by using empty OR outside their regular working hours to perform additional surgeries. As mentioned previously, such strategies are referred to as extended OR hours in this paper. A preliminary search of recent literature reviews devoted to OR planning and scheduling confirmed the lack of approaches related to extended OR hours ( 13 – 15 ).

On December 10, 2021, a systematic search was conducted on the Web of Science database with the following query:

(TS=(“healthcare”) OR TS=(“health care”) OR TS=(“care”) OR TS=(“operating room*”) OR TS=(“operating theat*”) OR TS=(“surg*”)) AND (TS=(“backlog”) OR TS=(“temporary capacity change”) OR TS=(“max* capacity”) OR TS=(“improve* use of existing capacity”) OR TS=(“capacity expan*”) OR TS=(“expand* capacity”) OR TS=(“increas* capacity”) OR TS=(“extra capacity”) OR TS=(“extra time”) OR TS=(“extratime”) OR TS=(“overtime”) OR TS=(“after-hours”) OR TS=(“after hours”) OR TS=(“outside work* hour*”) OR TS=(“extend* hour*”))

This search retrieved 3,721 results, of which 3,511 were written in English. Of those, we decided to exclude papers published before 2011, resulting in a final pool of 2,727 papers for analysis. Any paper mentioning planning strategies that involve either temporary change of service capacity or increasing working hours or flexibility of human resources to proactively increase productivity and reduce backlogs in healthcare by taking advantage of extended time was considered potentially relevant. We included not only surgical settings, but also non-surgical settings that operate in a similar way to the former, to increase the potential for finding extended time strategies. However, documents focused on emergency services were excluded on account of their 24/7 nature, which makes any separation between regular and extended hours irrelevant. No exclusion criteria regarding the quality or the type of document were applied. The document selection scheme is summarized in Figure 1 .

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Figure 1 . Document selection scheme used for the systematic review of the literature in the Web of Science database.

By screening titles and abstracts, the pool of documents was reduced to 89 papers. During this analysis, several research trends or topics were identified: impact of after-hours surgery or admission (mostly focused on trauma or emergency services), open scheduling, or extended opening for temporal convenience (usually associated with increasing business hours to reduce the number of people in emergency services). These research topics were discarded for the present literature review because they do not fit the extended OR hours scope. However, they contribute interesting discussions on the implications of introducing flexibility in schedules through the increase of working hours that, in our opinion, also apply to the extended OR hours context. After reading the 89 full documents, 12 papers were selected to be relevant as a result of this literature search.

Tables 1 , 2 summarize the main features and the contributions of the 12 papers resulting from the search described in the previous section. These tables include, for each paper, their Methodology (Metho.) and their setting, which encompasses the country (Count.), if the application was developed before or after the Covid-19 pandemic (Pre/Post), and the clinical specialty or service (Serv.). Then, the four next columns characterize the type of strategy it proposes. The first two of them are related to Increase Capacity (Inc. cap.), which includes Extended Hours (E.H.) and other approaches (Other), and the two following columns characterize Manage demand (Man. Dem.) and Increase Productivity (Incr. Prod.). The last column describes the paper's objective. Table 1 presents papers related to non-surgical settings, whereas Table 2 reports studies on surgical settings. These settings differ mostly on the resources required, which can, in turn, impact the strategy proposed. Surgical settings typically require specialized equipment along with a multidisciplinary team, which is not necessarily the case in other settings. Moreover, decisions on surgical settings extend beyond the OR, affecting, for instance, intensive care units and hospitalization units.

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Table 1 . Resulting papers concerning extended hours in non-surgical settings.

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Table 2 . Resulting papers concerning extended hours in surgical settings.

Among the 12 papers, we observed a variety of propositions that we grouped into three families of strategies: (1) strategies that seek to increase the opening hours of the corresponding service, including weekend and after-hour clinics; (2) strategies to better manage demand, including prioritization and triage, treatment postponement, and patient transfer; and (3) strategies to increase productivity, such as specific fee-for-services to reward physicians and reduced protocols. It is worth noting that several of the papers were published after March 2020, therefore after the beginning of the COVID-19 pandemic. These papers discuss strategies to resume services after lockdown. While the COVID-19 pandemic exacerbated waiting lists, we assume that similar strategies can be envisioned to address backlogs regardless of the situation (pre- or post-pandemic). Nevertheless, the volume of surgeries or services to be performed can be larger in a post-pandemic situation, and specific infection control methods can impact the time to provide service. Therefore, we deemed it important to identify if the study considered a pre- or post-COVID setting.

Table 1 contains four studies that analyze and discuss strategies to reduce waiting lists in non-surgical settings. These studies concern a variety of contexts in different countries, including primary care ( 16 , 18 ), outpatient clinics ( 17 , 18 ), hospital units ( 18 ), and imaging and radiology ( 19 ), and were conducted mostly before the COVID-19 pandemic ( 16 – 18 ). We observed that pre-COVID studies tend to perform deeper analysis and evaluations compared to post-COVID studies, in particular through data analysis. In the next paragraph, we present a detailed description of these studies, focusing on their objectives and key findings.

In 2011, Kantarevic et al. ( 16 ) described an enhanced fee-for-service model that encourages providers to improve patient access and quality of care through contractual extended service hours (evenings, weekends, and holidays) in the context of primary care in Canada. The enhanced fee-for-service model aims to increase productivity by rewarding doctors. Using an economic model, they showed that this new payment model increased primary care physician productivity, measured as the number of services provided and patients treated compared to typical fee-for-service reimbursement. Overall, the authors estimated productivity gains of 6–10%, corresponding to 2–3 weeks of additional work over a year.

Tan et al. ( 17 ) described a case study in which a working group was created to find ways to reduce long waiting times in the General Pediatric Clinic in Singapore in 2017. The implementation of weekend clinics to clear backlogs of outpatient referrals was one of the initiatives proposed by the group. This initiative targeted specifically patients with a waiting time longer than 60 days. The implementation of weekend clinics, together with other improvements such as, for example, a triage system, allowed the General Pediatric Clinic to reduce waiting times by 30%. The authors concluded that weekend clinics appear to be effective in reducing waiting times, but, at the same time, they highlighted the lack of existing guidelines on when to open and how to manage those extra clinics.

Fagefors et al. ( 18 ) conducted a survey in which Swedish healthcare managers were asked about the strategies they used to create short-term volume flexibility in healthcare capacity to cope with demand fluctuations. The study concerned a wide range of hospital units, including non-surgical and surgical units. Among the reported conclusions, the authors emphasize that managers preferred to plan fixed overtime rather than use it as a response to specific situations and use on-call staff to fill the schedule gaps. The authors also underline that the type of strategies to use depends on the type of care unit and services it offers (e.g., acute care or not).

Like many post-pandemic studies, Azam et al. ( 19 ) provided an open discussion based on the review of guidelines rather than a formal evaluation of strategies to develop a roadmap for radiology departments with the aim to resume non-urgent imaging studies and elective procedures. In particular, they stress the importance of taking into account the context raised by COVID-19 to adapt practices, including specific infection control measures. However, to reduce backlogs, they suggested relying on extended hours of operation and extended shifts for radiologists. They highlighted that the implementation of such practices should be staged, incremental and regularly reviewed, and, at the same time, communication and transparency are required.

Table 2 presents the eight studies grounded in surgical settings. These studies considered various types of elective surgical settings, including general surgery, cataract, orthopedic, and laparoscopic cholecystectomy, and all but one were conducted in the UK and the US after the COVID-19 pandemic. In addition to the families of strategies presented, these papers also addressed several COVID-related measures, such as dedicated COVID-19 facilities and supplying of personal protective equipment. However, these measures are not discussed in the ensuing text since they are unrelated to extended OR hours. It is possible to observe that few of the papers include data analysis with a specific objective. In fact, most papers would rather include a discussion on ways to return to normal operations after COVID-19. In the next paragraphs, we first discuss papers that provide data analysis and then highlight key intakes from discussion papers.

Bhuiyan and Mavhungu ( 20 ) is the only paper in a surgical setting published before the COVID-19 pandemic. In this paper, the authors recommended Saturday elective surgeries for a hospital in South Africa as a course to maximize the use of OR in all tertiary hospitals that do not have a daytime emergency room or/and long waiting times. This study assessed the quality of surgeries performed on Saturday—by computing the death rate within 30 days for patients having received their surgery on Saturday—as well as the cost of performing those surgeries. Based on a prospective observational descriptive cohort study, it concluded that surgeries performed on Saturday have an associated death rate of 1.5% (compared to 1.9% on weekdays) and an additional cost of between ZAR 2,317 to 3,450 per patient to cover overtime costs. However, the authors suggested that high-risk patients should have their surgery performed on weekdays. Saturday patients, therefore, need to be selected carefully, confirming the effectiveness of extended OR hours, but raising a key question on how these should be used.

Using data published by NHS Digital and NHS England, Macdonald et al. ( 22 ) estimated the number of cancellations and missed cases of elective surgeries due to COVID-19. The authors concluded that surgery backlogs were rising even before the COVID-19 pandemic. They also stated that weekend working is well-defined in the National Health System, and it has been a successful temporary strategy that, although requiring additional funds, is able to reduce waiting times. Moreover, it is also recommended that adding a third session to the OR can constitute an option to replace the capacity loss due to time-consuming COVID-19 safety protocols.

Clifford et al. ( 26 ) analyzed data on financial implications, demographics, procedures and outcomes after and before the implementation of five intensive dedicated operating lists (i.e., waiting lists deliberately created to address backlogs) for laparoscopic cholecystectomies on weekends in October 2020 at a single Trust. The analysis demonstrated the benefits of performing weekend surgeries, rapidly reducing waiting lists for laparoscopic cholecystectomy elective surgery after COVID-19. However, the authors recommended a careful selection of patients, which should be done by a multidisciplinary team.

Lin and Chou ( 21 ) proposed care providers to develop a new patient-centered clinical pathway by redesigning the cataract service in the post-COVID-19 era. One of the proposals they discussed is the possibility of considering routine cataract integrated practice units with high volume weekend/evening following independent patient lists. Moawad et al. ( 23 ) presented a perspective paper proposing to extend surgical hours on weekdays to increase OR access to resume elective surgical activity after the COVID-19 suspensions. In a letter to the editor, Samson ( 24 ) quantified the amount of additional OR hours, or the required extra shifts to be added to daily schedules, to compensate for the cancellation of cases due to the COVID-19 pandemic. The author stressed the fact that overtime undermines the performance of OR staff, encouraging managers to be prudent on its usage. In addition, it is suggested to rely on retired medical professionals to increase regular staff, and, finally, it is recommended to allow additional 8-hour OR shifts in the evenings or on weekends. Anastasio et al. ( 25 ) wrote a commentary note suggesting after-hours surgery as a timely and cost-effective strategy to deal with backlogs due to the COVID-19 shutdown, but also alerted to the potential consequences of staff exhaustion. To mitigate this, it was suggested to form dedicated nighttime surgical teams, ensuring them rest time during the day.

Finally, Barie et al. ( 27 ) reviewed and summarized peer-reviewed literature, while integrating it with expert opinion on guidelines for resuming surgical services during the COVID-19 pandemic, to improve outcomes and safety, preserve resources, reduce costs and ultimately reduce surgical backlogs. Besides key points, such as institutional commitment, structural programs, equitable implementation, audits, and planning and integration, the authors stressed that case prioritization during the resumption of services needs to consider surgical risk factors, COVID-19-related risks and facility capacity, through the maximization of the capacity of outpatient facilities and the use of off-hours.

The utilization of unused OR time, such as after-hours or weekends, to increase capacity and, eventually, reduce backlogs, has been suggested in the literature. However, while interest in this type of strategy has grown as a result of the worldwide suspension of elective surgeries during COVID-19, its potential in reducing waiting lists has only been studied superficially. Indeed, there is a lack of models, case studies, and guidelines that might help managers develop and implement extended OR hours strategies at a time when they might make a difference. Moreover, during the development of this literature review, a gap was evident in terms of the discussion of key decisions in such a context and their impact on patients, staff, and the health system in general. Nevertheless, two main insights come from those papers. First, they acknowledge that extended hours, either after-hours or weekends, could be problematic if current staff is used, leading to fatigue, overload, and burden. Therefore, we need to find ways to recruit staff (e.g., retired clinicians, having dedicated staff, etc.). Second, patients to be operated on need to be chosen carefully. These issues and other questions that we deemed central to the deployment of extended OR hours strategies are discussed in the next section.

4. Discussion

The pressure on health systems worldwide to deliver appropriate care has never been so high. In the case of surgical services, the reduction of activity imposed by the COVID-19 pandemic exacerbated an already existing problem of extensive backlogs, which result in a drastic deterioration of the access time to surgeries. We have identified two main goals inspiring the reviewed research papers: resuming activity post-COVID (i.e., defining guidelines for isolation pathways, safety protocols, prioritization or treatment simplification), and increasing capacity or extending service hours, although no study thoroughly assesses their impact and implications.

We believe that both goals are strongly affected by the fact that human resources are even scarcer than before the pandemic, given that the entire health system is exhausted by this fight and OR staff have been deployed to reinforce services in deeper need. Therefore, recovering the pre-pandemic staffing levels seems rather optimistic, at least in the short term. Meanwhile, managers must carefully analyze the extent to which backlogs have been originated by structural (permanent offer to demand unbalance) or transient (the pandemic) reasons to decide on the set of actions to take.

To shed some light on the complex decisions related to extended OR hours, the next subsections review some crucial aspects, grouped into four categories: the management, the staff, the patients, and the deployment of the strategy. We believe these are the aspects managers should ponder when formalizing their extended OR hours strategy.

4.1. The management

Extended OR hours may allow hospitals to increase their financing and/or avoid penalties, in case their funding is tied to performance targets. However, additional surgeries also require additional costs, thus, their profitability needs to be assessed and the contribution margin must be considered in the specific situation of each hospital. Sutherland ( 28 ) described the case of hospitals in British Columbia (Canada) that received financial incentives to increase surgical volume through marginal pricing approaches and analyzed four scenarios that represent situations with decreasing workforce availability. The first scenario corresponded to staff overcapacity, so the available staff is able to perform more surgeries. In the second scenario, staffing was adequate, but it was assumed that improvements in efficiency allowed to increase the number of performed surgeries. The remaining scenarios considered undercapacity: in the third scenario, the hospital used overtime to increase the number of surgeries, whereas in the fourth scenario premium rates were paid. Sutherland ( 28 ) concluded that, in order to be efficient, strategies and specific financial incentives need to be adjusted according to the underlying cost structures of the hospital. Specifically, since some surgical cases are more profitable than others, it is important to establish guidelines and mechanisms that ensure that the economic criterion is not the only one considered in allocating the extra time to specialties. In the same vein, managers must be aware that the incentives and rewards associated with activities in extended OR hours might create competition between the hospital services or departments.

4.2. The staff

Extended OR hours require a voluntary engagement of staff, who offer to work on specific days and/or time slots which are outside their regular working hours. Therefore, staff needs to be adequately compensated or rewarded for their additional effort. Rewards for extra work typically include extra time off, promotion, recognition and financial rewards ( 29 ). However, Broadway et al. ( 30 ) showed that economic rewards alone are ineffective in promoting engagement in after-hours work and may even be harmful if incentives are not properly targeted. Almaghrabi et al. ( 31 ) conducted a web-based survey to healthcare workers to assess their willingness to work overtime and extra hours during the COVID-19 pandemic. The results demonstrated a high positive response and engagement, confirming that, when the situation calls for it, health workers are open to working out of their regular schedules to achieve a certain goal. This result shows why the communication of the aim of the strategy is so important to its success. Note, however, that if too many workers are willing to fill in extended hours, managers must allocate the extra time in a fair and transparent manner to preserve the motivation and the engagement of the workers.

Another important aspect of extended OR hours, which has also been discussed in Section 3, is that it might have a negative impact on the workers' performance, as well as on their health, safety, and wellbeing. Lobo et al. ( 32 ) reported that nurses working overtime suffer more injury hazards and have less ability to achieve a good work-life balance, while Stimpfel et al. ( 33 ) account that newly licensed nurses working weekly overtime are associated with a higher risk of needle stick. As an advantage, voluntary overtime hours seem to reduce turnover among nurses ( 34 ). Although these papers refer to overtime and not extended OR hours, both strategies share the trait of involving surgical staff working additional hours, which might lead to reduced quality of life for these hospital workers.

4.3. The patients

Increasing the number of surgeries performed is clearly aligned with the needs of patients. However, throughput is not the only goal to pursue. In fact, extended OR hours strategies should be patient-centered, although some studies have shown that nurses working overtime are more task-oriented than patient-centered in the care they provide ( 32 ). Promoting teamwork and assuring that all the members are engaged in a patient safety culture should be one of the priorities in managing extended capacity since, as Cortegiani et al. ( 35 ) showed in the systematic review and meta-analysis that they performed, night and after-hours surgeries, when used to reduce waiting lists, are associated with a higher adjusted risk of mortality when compared to surgeries performed during daytime, even though the existent evidence is weak. Additionally, as mentioned in Section 3, discussing criteria for choosing patients to be scheduled on extended hours and establishing adequate work guidelines is fundamental.

4.4. Deploying the strategy

Planning extended OR hours can be as complex as planning regular hours. In fact, similar decisions have to be taken, although potentially for different objectives and subject to different restrictions. For instance, managers must decide how many extended hours to add and also when to add them, given the regular fixed OR hours. Decisions regarding which specialties should access the extra time or how the extra time should be shared among the specialties are also similarly important in both regular and extended OR hours. Nevertheless, extended OR hours should be more flexible than the regular hours defined by the MSS, allowing the hospital to relax some constraints that limit their decisions, such as, for instance, guaranteeing a minimum number of weekly or monthly hours to each specialty. On the other hand, the assignment of staff to extended OR hours is harder than in the case of regular hours, since the staff must voluntarily agree to work these extended hours.

To handle the above-mentioned difficulties, at least two alternative models for the implementation of extended OR hours can be envisaged: a hierarchical model where the hospital plans and manages the extended OR hours as a second MSS, and a second, more participatory, bottom-up model where each service or specialty proposes additional working hours to the hospital managers, who decide the access to extended OR hours according to the established goals and mechanisms. The latter approach offers an important advantage, since it simplifies the negotiations with the staff, who self-organize into teams to elaborate proposals for the use of extended hours.

Regardless of the model used to implement extended OR hours, we would like to stress the importance of performance measurement and monitoring, for two main reasons. First, it is imperative to ensure that the extended OR hours are successfully addressing the underlying problem to be solved, namely that of reducing the extensive backlogs of patients. Second, it is also important to guarantee that regular hours activities are not negatively impacted by extended OR hours, since the latter are only complementary to the former and, thus, should not serve as a replacement.

4.5. Conclusions

Based on the lessons learned from the reviewed papers and our experience and discussions with healthcare managers, we would like to propose three recommendations we deem necessary, yet insufficient, for successfully implementing extended OR hours strategies.

The first recommendation is that extended OR hours, as defined in this paper (i.e., using existing human resources), should only be used in the short term or, if used in medium to long terms, its intensity should be limited to prevent exhaustion of the OR staff and the post-surgical services, which might be overloaded.

The second recommendation stresses the need for a shared understanding and agreement of all the stakeholders on the goals pursued by this strategy: is it to broaden access to services?, is it to cope with emergency surgeries?, is it to perform more surgeries of a particular type?, or is it to treat specific patients under specific situations? Only after all the stakeholders (managers, staff, and patients) have agreed on the objectives, it is possible to start framing and planning how to make the best use of extended OR hours.

The third recommendation concerns communication and transparency. Decisions should be clear and communicated to all stakeholders. This level of transparency allows decisions to be revised in light of information held by different people. Indeed, if decision-makers share the knowledge about the strategic goal of extended OR hours, it should be easier to guarantee an efficient and fair use of resources.

Although the future trends of research on extended operating room hours can take different directions, the authors recommend exploring three specific topics that can be particularly promising for future research: enquiring on the professional's motivations and the rewards that matter to them, the development of methods to quantify the “value” of a given surgery for the organization, and the study of approach to mutualize or share hospital's capacity.

Elective surgical patient backlogs constitute a challenge for healthcare organizations and may lead to the adoption of extended operating room hours to perform additional surgeries. However, extending working hours requires understanding what motivates healthcare professionals, including surgeons, nurses and anesthetists, to accept such an arrangement. Studies that assess what may motivate healthcare professional, such as financial incentives, downtime or other work benefits, are particularly encouraged. Those results will allow healthcare managers to plan, identify and quantify rewards that maximize surgical staff's satisfaction whilst reducing the risk of burnout, which is more critical than ever in healthcare.

Decisions regarding which surgeries to perform during extended operating hours should be made based on their value, which includes but it is not limited to the associated revenue. For instance, value should consider medical risks and penalties for delayed surgeries, and eventually capture the surgery's impact on the patients' quality of life. Therefore, determining the value of each surgery is pivotal when managing extended operating room hours, and should be used by decision support systems to assist managers in the selection of surgeries to maximize total value at the time that a fair access to extended time to all the specialties and professional is guaranteed.

Furthermore, hospitals should work together as a network to offer available operating room time to other organizations or exchange surgeries to minimize delays and increase patient and stakeholders' satisfaction. This approach can help to redistribute surgical demand across healthcare facilities and reduce wait times. However, it is crucial to develop a fair and equitable system to allocate operating room time among healthcare organizations and clearly set the rules for transferring patients. Research into the feasibility and effectiveness of such a network-based approach is necessary to optimize surgical care delivery.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Author contributions

All authors contributed equally to the research design, development, and manuscript writing. All authors contributed to the article and approved the submitted version.

This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), through the Discovery Grants Program, Grant 2020-07055, and by Portuguese National Funding from FCT - Fundação para a Ciência e a Tecnologia, under projects LAIfeBlood - Artificial Intelligence for Blood Management (DSAIPA/AI/0033/2019), PTDC/EGEOGE/30442/2017-Lisboa-01.0145-Feder-30442 and CEGIST - UIDB/00097/2020, and a PhD scholarship with reference 2020.09648.BD.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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Keywords: healthcare, hospital management, operating room planning and scheduling, elective patients, surgical backlogs, extended hours

Citation: Oliveira M, Bélanger V, Ruiz A and Santos D (2023) A systematic literature review on the utilization of extended operating room hours to reduce surgical backlogs. Front. Public Health 11:1118072. doi: 10.3389/fpubh.2023.1118072

Received: 07 December 2022; Accepted: 17 March 2023; Published: 13 April 2023.

Reviewed by:

Copyright © 2023 Oliveira, Bélanger, Ruiz and Santos. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Mariana Oliveira, mariana.m.oliveira@tecnico.ulisboa.pt

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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  1. How to Write a Literature Review

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  2. Chapter 9 Methods for Literature Reviews

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  3. Writing a Literature Review

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  4. Literature review as a research methodology: An overview and guidelines

    1. Introduction Building your research on and relating it to existing knowledge is the building block of all academic research activities, regardless of discipline. Therefore, to do so accurately should be a priority for all academics. However, this task has become increasingly complex.

  5. Steps in Conducting a Literature Review

    A literature review is an integrated analysis-- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

  6. PDF METHODOLOGY OF THE LITERATURE REVIEW

    The literature review represents a method because the literature reviewer chooses from an array of strategies and procedures for identifying, recording, understanding, meaning-making, and transmitting information pertinent to a topic of interest.

  7. Methodological Approaches to Literature Review

    Methodological Approaches to Literature Review Dennis Thomas, Elida Zairina & Johnson George Living reference work entry First Online: 09 May 2023 269 Accesses Abstract The literature review can serve various functions in the contexts of education and research.

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    Literature review is an essential feature of academic research. Fundamentally, knowledge advancement must be built on prior existing work. To push the knowledge frontier, we must know where the frontier is. By reviewing relevant literature, we understand the breadth and depth of the existing body of work and identify gaps to explore.

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  10. Research Methods: Literature Reviews

    Steps Research: locate literature related to your topic to identify the gap (s) that can be addressed Read: read the articles or other sources of information Analyze: assess the findings for relevancy Evaluating: determine how the article are relevant to your research and what are the key findings

  11. Ten Simple Rules for Writing a Literature Review

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  12. Types of literature review, methods, & resources

    Health information and libraries journal, 36(3), 202-222. doi:10.1111/hir.12276 (An updated look at different types of literature review, expands on the Grant & Booth 2009 article listed above). Garrard, J. (2007). Health Sciences Literature Review Made Easy: The Matrix Method (2nd Ed.). Sudbury, MA: Jones & Bartlett Publishers. (Textbook of ...

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  14. What is a Literature Review?

    Step 1: Search for relevant literature Step 2: Evaluate and select sources Step 3: Identify themes, debates and gaps Step 4: Outline your literature review's structure Step 5: Write your literature review Frequently asked questions about literature reviews Introduction Quick Run-through Step 1 & 2 Step 3 Step 4 Step 5 Why write a literature review?

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  18. Types of Literature Reviews

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    The conventional focus of rigorous literature reviews (i.e., review types for which systematic methods have been codified, including the various approaches to quantitative systematic reviews [2-4], and the numerous forms of qualitative and mixed methods literature synthesis [5-10]) is to synthesize empirical research findings from multiple ...

  20. An overview of methodological approaches in systematic reviews

    1. INTRODUCTION. Evidence synthesis is a prerequisite for knowledge translation. 1 A well conducted systematic review (SR), often in conjunction with meta‐analyses (MA) when appropriate, is considered the "gold standard" of methods for synthesizing evidence related to a topic of interest. 2 The central strength of an SR is the transparency of the methods used to systematically search ...

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