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

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.

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See an example

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.

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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Methodological Approaches to Literature Review

• Living reference work entry
• First Online: 09 May 2023
• Cite this living reference work entry

• Dennis Thomas 2 ,
• Elida Zairina 3 &
• Johnson George 4  

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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.

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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

Elida Zairina

Centre for Medicine Use and Safety, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia

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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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Literature Reviews

Steps in the literature review process.

• What is a literature review?
• Define your research question
• Determine inclusion and exclusion criteria
• Choose databases and search
• Review Results
• Synthesize Results
• Analyze Results
• Librarian Support
• You may need to some exploratory searching of the literature to get a sense of scope, to determine whether you need to narrow or broaden your focus
• Identify databases that provide the most relevant sources, and identify relevant terms (controlled vocabularies) to add to your search strategy
• Finalize your research question
• Think about relevant dates, geographies (and languages), methods, and conflicting points of view
• Conduct searches in the published literature via the identified databases
• Check to see if this topic has been covered in other discipline's databases
• Examine the citations of on-point articles for keywords, authors, and previous research (via references) and cited reference searching.
• Save your search results in a citation management tool (such as Zotero, Mendeley or EndNote)
• De-duplicate your search results
• Make sure that you've found the seminal pieces -- they have been cited many times, and their work is considered foundational 
• Check with your professor or a librarian to make sure your search has been comprehensive
• Evaluate the strengths and weaknesses of individual sources and evaluate for bias, methodologies, and thoroughness
• Group your results in to an organizational structure that will support why your research needs to be done, or that provides the answer to your research question  
• Develop your conclusions
• Are there gaps in the literature?
• Where has significant research taken place, and who has done it?
• Is there consensus or debate on this topic?
• Which methodological approaches work best?
• For example: Background, Current Practices, Critics and Proponents, Where/How this study will fit in 
• Organize your citations and focus on your research question and pertinent studies
• Compile your bibliography

Note: The first four steps are the best points at which to contact a librarian. Your librarian can help you determine the best databases to use for your topic, assess scope, and formulate a search strategy.

Videos Tutorials about Literature Reviews

This 4.5 minute video from Academic Education Materials has a Creative Commons License and a British narrator.

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• Last Updated: Oct 26, 2022 2:49 PM
• URL: https://guides.lib.utexas.edu/literaturereviews

Research Process :: Step by Step

• Introduction
• Select Topic
• Identify Keywords
• Background Information
• Develop Research Questions
• Refine Topic
• Search Strategy
• Popular Databases
• Evaluate Sources
• Types of Periodicals
• Reading Scholarly Articles
• Primary & Secondary Sources
• Organize / Take Notes
• Writing & Grammar Resources
• Annotated Bibliography
• Literature Review
• Citation Styles
• Paraphrasing
• Privacy / Confidentiality
• Research Process
• Selecting Your Topic
• Identifying Keywords
• Gathering Background Info
• Evaluating Sources

Organize the literature review into sections that present themes or identify trends, including relevant theory. You are not trying to list all the material published, but to synthesize and evaluate it according to the guiding concept of your thesis or research question.  

What is a literature review?

A literature review is an account of what has been published on a topic by accredited scholars and researchers. Occasionally you will be asked to write one as a separate assignment, but more often it is part of the introduction to an essay, research report, or thesis. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries

A literature review must do these things:

• be organized around and related directly to the thesis or research question you are developing
• synthesize results into a summary of what is and is not known
• identify areas of controversy in the literature
• formulate questions that need further research

Ask yourself questions like these:

• What is the specific thesis, problem, or research question that my literature review helps to define?
• What type of literature review am I conducting? Am I looking at issues of theory? methodology? policy? quantitative research (e.g. on the effectiveness of a new procedure)? qualitative research (e.g., studies of loneliness among migrant workers)?
• What is the scope of my literature review? What types of publications am I using (e.g., journals, books, government documents, popular media)? What discipline am I working in (e.g., nursing psychology, sociology, medicine)?
• How good was my information seeking? Has my search been wide enough to ensure I've found all the relevant material? Has it been narrow enough to exclude irrelevant material? Is the number of sources I've used appropriate for the length of my paper?
• Have I critically analyzed the literature I use? Do I follow through a set of concepts and questions, comparing items to each other in the ways they deal with them? Instead of just listing and summarizing items, do I assess them, discussing strengths and weaknesses?
• Have I cited and discussed studies contrary to my perspective?
• Will the reader find my literature review relevant, appropriate, and useful?

Ask yourself questions like these about each book or article you include:

• Has the author formulated a problem/issue?
• Is it clearly defined? Is its significance (scope, severity, relevance) clearly established?
• Could the problem have been approached more effectively from another perspective?
• What is the author's research orientation (e.g., interpretive, critical science, combination)?
• What is the author's theoretical framework (e.g., psychological, developmental, feminist)?
• What is the relationship between the theoretical and research perspectives?
• Has the author evaluated the literature relevant to the problem/issue? Does the author include literature taking positions she or he does not agree with?
• In a research study, how good are the basic components of the study design (e.g., population, intervention, outcome)? How accurate and valid are the measurements? Is the analysis of the data accurate and relevant to the research question? Are the conclusions validly based upon the data and analysis?
• In material written for a popular readership, does the author use appeals to emotion, one-sided examples, or rhetorically-charged language and tone? Is there an objective basis to the reasoning, or is the author merely "proving" what he or she already believes?
• How does the author structure the argument? Can you "deconstruct" the flow of the argument to see whether or where it breaks down logically (e.g., in establishing cause-effect relationships)?
• In what ways does this book or article contribute to our understanding of the problem under study, and in what ways is it useful for practice? What are the strengths and limitations?
• How does this book or article relate to the specific thesis or question I am developing?

Text written by Dena Taylor, Health Sciences Writing Centre, University of Toronto

http://www.writing.utoronto.ca/advice/specific-types-of-writing/literature-review

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Types of Literature Review — A Guide for Researchers

Table of Contents

Researchers often face challenges when choosing the appropriate type of literature review for their study. Regardless of the type of research design and the topic of a research problem , they encounter numerous queries, including:

What is the right type of literature review my study demands?

• How do we gather the data?
• How to conduct one?
• How reliable are the review findings?
• How do we employ them in our research? And the list goes on.

If you’re also dealing with such a hefty questionnaire, this article is of help. Read through this piece of guide to get an exhaustive understanding of the different types of literature reviews and their step-by-step methodologies along with a dash of pros and cons discussed.

Heading from scratch!

What is a Literature Review?

A literature review provides a comprehensive overview of existing knowledge on a particular topic, which is quintessential to any research project. Researchers employ various literature reviews based on their research goals and methodologies. The review process involves assembling, critically evaluating, and synthesizing existing scientific publications relevant to the research question at hand. It serves multiple purposes, including identifying gaps in existing literature, providing theoretical background, and supporting the rationale for a research study.

What is the importance of a Literature review in research?

Literature review in research serves several key purposes, including:

• Background of the study: Provides proper context for the research. It helps researchers understand the historical development, theoretical perspectives, and key debates related to their research topic.
• Identification of research gaps: By reviewing existing literature, researchers can identify gaps or inconsistencies in knowledge, paving the way for new research questions and hypotheses relevant to their study.
• Theoretical framework development: Facilitates the development of theoretical frameworks by cultivating diverse perspectives and empirical findings. It helps researchers refine their conceptualizations and theoretical models.
• Methodological guidance: Offers methodological guidance by highlighting the documented research methods and techniques used in previous studies. It assists researchers in selecting appropriate research designs, data collection methods, and analytical tools.
• Quality assurance and upholding academic integrity: Conducting a thorough literature review demonstrates the rigor and scholarly integrity of the research. It ensures that researchers are aware of relevant studies and can accurately attribute ideas and findings to their original sources.

Types of Literature Review

Literature review plays a crucial role in guiding the research process , from providing the background of the study to research dissemination and contributing to the synthesis of the latest theoretical literature review findings in academia.

However, not all types of literature reviews are the same; they vary in terms of methodology, approach, and purpose. Let's have a look at the various types of literature reviews to gain a deeper understanding of their applications.

1. Narrative Literature Review

A narrative literature review, also known as a traditional literature review, involves analyzing and summarizing existing literature without adhering to a structured methodology. It typically provides a descriptive overview of key concepts, theories, and relevant findings of the research topic.

Unlike other types of literature reviews, narrative reviews reinforce a more traditional approach, emphasizing the interpretation and discussion of the research findings rather than strict adherence to methodological review criteria. It helps researchers explore diverse perspectives and insights based on the research topic and acts as preliminary work for further investigation.

Steps to Conduct a Narrative Literature Review

Source:- https://www.researchgate.net/figure/Steps-of-writing-a-narrative-review_fig1_354466408

Define the research question or topic:

The first step in conducting a narrative literature review is to clearly define the research question or topic of interest. Defining the scope and purpose of the review includes — What specific aspect of the topic do you want to explore? What are the main objectives of the research? Refine your research question based on the specific area you want to explore.

Conduct a thorough literature search

Once the research question is defined, you can conduct a comprehensive literature search. Explore and use relevant databases and search engines like SciSpace Discover to identify credible and pertinent, scholarly articles and publications.

Select relevant studies

Before choosing the right set of studies, it’s vital to determine inclusion (studies that should possess the required factors) and exclusion criteria for the literature and then carefully select papers. For example — Which studies or sources will be included based on relevance, quality, and publication date?

*Important (applies to all the reviews): Inclusion criteria are the factors a study must include (For example: Include only peer-reviewed articles published between 2022-2023, etc.). Exclusion criteria are the factors that wouldn’t be required for your search strategy (Example: exclude irrelevant papers, preprints, written in non-English, etc.)

Critically analyze the literature

Once the relevant studies are shortlisted, evaluate the methodology, findings, and limitations of each source and jot down key themes, patterns, and contradictions. You can use efficient AI tools to conduct a thorough literature review and analyze all the required information.

Synthesize and integrate the findings

Now, you can weave together the reviewed studies, underscoring significant findings such that new frameworks, contrasting viewpoints, and identifying knowledge gaps.

Discussion and conclusion

This is an important step before crafting a narrative review — summarize the main findings of the review and discuss their implications in the relevant field. For example — What are the practical implications for practitioners? What are the directions for future research for them?

Write a cohesive narrative review

Organize the review into coherent sections and structure your review logically, guiding the reader through the research landscape and offering valuable insights. Use clear and concise language to convey key points effectively.

Structure of Narrative Literature Review

A well-structured, narrative analysis or literature review typically includes the following components:

• Introduction: Provides an overview of the topic, objectives of the study, and rationale for the review.
• Background: Highlights relevant background information and establish the context for the review.
• Main Body: Indexes the literature into thematic sections or categories, discussing key findings, methodologies, and theoretical frameworks.
• Discussion: Analyze and synthesize the findings of the reviewed studies, stressing similarities, differences, and any gaps in the literature.
• Conclusion: Summarizes the main findings of the review, identifies implications for future research, and offers concluding remarks.

Pros and Cons of Narrative Literature Review

• Flexibility in methodology and doesn’t necessarily rely on structured methodologies
• Follows traditional approach and provides valuable and contextualized insights
• Suitable for exploring complex or interdisciplinary topics. For example — Climate change and human health, Cybersecurity and privacy in the digital age, and more
• Subjectivity in data selection and interpretation
• Potential for bias in the review process
• Lack of rigor compared to systematic reviews

Example of Well-Executed Narrative Literature Reviews

Paper title:  Examining Moral Injury in Clinical Practice: A Narrative Literature Review

Source: SciSpace

While narrative reviews offer flexibility, academic integrity remains paramount. So, ensure proper citation of all sources and maintain a transparent and factual approach throughout your critical narrative review, itself.

2. Systematic Review

A systematic literature review is one of the comprehensive types of literature review that follows a structured approach to assembling, analyzing, and synthesizing existing research relevant to a particular topic or question. It involves clearly defined criteria for exploring and choosing studies, as well as rigorous methods for evaluating the quality of relevant studies.

It plays a prominent role in evidence-based practice and decision-making across various domains, including healthcare, social sciences, education, health sciences, and more. By systematically investigating available literature, researchers can identify gaps in knowledge, evaluate the strength of evidence, and report future research directions.

Steps to Conduct Systematic Reviews

Source:- https://www.researchgate.net/figure/Steps-of-Systematic-Literature-Review_fig1_321422320

Here are the key steps involved in conducting a systematic literature review

Formulate a clear and focused research question

Clearly define the research question or objective of the review. It helps to centralize the literature search strategy and determine inclusion criteria for relevant studies.

Develop a thorough literature search strategy

Design a comprehensive search strategy to identify relevant studies. It involves scrutinizing scientific databases and all relevant articles in journals. Plus, seek suggestions from domain experts and review reference lists of relevant review articles.

Screening and selecting studies

Employ predefined inclusion and exclusion criteria to systematically screen the identified studies. This screening process also typically involves multiple reviewers independently assessing the eligibility of each study.

Data extraction

Extract key information from selected studies using standardized forms or protocols. It includes study characteristics, methods, results, and conclusions.

Critical appraisal

Evaluate the methodological quality and potential biases of included studies. Various tools (BMC medical research methodology) and criteria can be implemented for critical evaluation depending on the study design and research quetions .

Data synthesis

Analyze and synthesize review findings from individual studies to draw encompassing conclusions or identify overarching patterns and explore heterogeneity among studies.

Interpretation and conclusion

Interpret the findings about the research question, considering the strengths and limitations of the research evidence. Draw conclusions and implications for further research.

The final step — Report writing

Craft a detailed report of the systematic literature review adhering to the established guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). This ensures transparency and reproducibility of the review process.

By following these steps, a systematic literature review aims to provide a comprehensive and unbiased summary of existing evidence, help make informed decisions, and advance knowledge in the respective domain or field.

Structure of a systematic literature review

A well-structured systematic literature review typically consists of the following sections:

• Introduction: Provides background information on the research topic, outlines the review objectives, and enunciates the scope of the study.
• Methodology: Describes the literature search strategy, selection criteria, data extraction process, and other methods used for data synthesis, extraction, or other data analysis..
• Results: Presents the review findings, including a summary of the incorporated studies and their key findings.
• Discussion: Interprets the findings in light of the review objectives, discusses their implications, and identifies limitations or promising areas for future research.
• Conclusion: Summarizes the main review findings and provides suggestions based on the evidence presented in depth meta analysis.

*Important (applies to all the reviews): Remember, the specific structure of your literature review may vary depending on your topic, research question, and intended audience. However, adhering to a clear and logical hierarchy ensures your review effectively analyses and synthesizes knowledge and contributes valuable insights for readers.

Pros and Cons of Systematic Literature Review

• Adopts rigorous and transparent methodology
• Minimizes bias and enhances the reliability of the study
• Provides evidence-based insights
• Time and resource-intensive
• High dependency on the quality of available literature (literature research strategy should be accurate)
• Potential for publication bias

Example of Well-Executed Systematic Literature Review

Paper title: Systematic Reviews: Understanding the Best Evidence For Clinical Decision-making in Health Care: Pros and Cons.

Read this detailed article on how to use AI tools to conduct a systematic review for your research!

3. Scoping Literature Review

A scoping literature review is a methodological review type of literature review that adopts an iterative approach to systematically map the existing literature on a particular topic or research area. It involves identifying, selecting, and synthesizing relevant papers to provide an overview of the size and scope of available evidence. Scoping reviews are broader in scope and include a diverse range of study designs and methodologies especially focused on health services research.

The main purpose of a scoping literature review is to examine the extent, range, and nature of existing studies on a topic, thereby identifying gaps in research, inconsistencies, and areas for further investigation. Additionally, scoping reviews can help researchers identify suitable methodologies and formulate clinical recommendations. They also act as the frameworks for future systematic reviews or primary research studies.

Scoping reviews are primarily focused on —

• Emerging or evolving topics — where the research landscape is still growing or budding. Example — Whole Systems Approaches to Diet and Healthy Weight: A Scoping Review of Reviews .
• Broad and complex topics : With a vast amount of existing literature.
• Scenarios where a systematic review is not feasible: Due to limited resources or time constraints.

Steps to Conduct a Scoping Literature Review

While Scoping reviews are not as rigorous as systematic reviews, however, they still follow a structured approach. Here are the steps:

Identify the research question: Define the broad topic you want to explore.

Identify Relevant Studies: Conduct a comprehensive search of relevant literature using appropriate databases, keywords, and search strategies.

Select studies to be included in the review: Based on the inclusion and exclusion criteria, determine the appropriate studies to be included in the review.

Data extraction and charting : Extract relevant information from selected studies, such as year, author, main results, study characteristics, key findings, and methodological approaches.  However, it varies depending on the research question.

Collate, summarize, and report the results: Analyze and summarize the extracted data to identify key themes and trends. Then, present the findings of the scoping review in a clear and structured manner, following established guidelines and frameworks .

Structure of a Scoping Literature Review

A scoping literature review typically follows a structured format similar to a systematic review. It includes the following sections:

• Introduction: Introduce the research topic and objectives of the review, providing the historical context, and rationale for the study.
• Methods : Describe the methods used to conduct the review, including search strategies, study selection criteria, and data extraction procedures.
• Results: Present the findings of the review, including key themes, concepts, and patterns identified in the literature review.
• Discussion: Examine the implications of the findings, including strengths, limitations, and areas for further examination.
• Conclusion: Recapitulate the main findings of the review and their implications for future research, policy, or practice.

Pros and Cons of Scoping Literature Review

• Provides a comprehensive overview of existing literature
• Helps to identify gaps and areas for further research
• Suitable for exploring broad or complex research questions
• Doesn’t provide the depth of analysis offered by systematic reviews
• Subject to researcher bias in study selection and data extraction
• Requires careful consideration of literature search strategies and inclusion criteria to ensure comprehensiveness and validity.

In short, a scoping review helps map the literature on developing or emerging topics and identifying gaps. It might be considered as a step before conducting another type of review, such as a systematic review. Basically, acts as a precursor for other literature reviews.

Example of a Well-Executed Scoping Literature Review

Paper title: Health Chatbots in Africa Literature: A Scoping Review

Check out the key differences between Systematic and Scoping reviews — Evaluating literature review: systematic vs. scoping reviews

4. Integrative Literature Review

Integrative Literature Review (ILR) is a type of literature review that proposes a distinctive way to analyze and synthesize existing literature on a specific topic, providing a thorough understanding of research and identifying potential gaps for future research.

Unlike a systematic review, which emphasizes quantitative studies and follows strict inclusion criteria, an ILR embraces a more pliable approach. It works beyond simply summarizing findings — it critically analyzes, integrates, and interprets research from various methodologies (qualitative, quantitative, mixed methods) to provide a deeper understanding of the research landscape. ILRs provide a holistic and systematic overview of existing research, integrating findings from various methodologies. ILRs are ideal for exploring intricate research issues, examining manifold perspectives, and developing new research questions.

Steps to Conduct an Integrative Literature Review

• Identify the research question: Clearly define the research question or topic of interest as formulating a clear and focused research question is critical to leading the entire review process.
• Literature search strategy: Employ systematic search techniques to locate relevant literature across various databases and sources.
• Evaluate the quality of the included studies : Critically assess the methodology, rigor, and validity of each study by applying inclusion and exclusion criteria to filter and select studies aligned with the research objectives.
• Data Extraction: Extract relevant data from selected studies using a structured approach.
• Synthesize the findings : Thoroughly analyze the selected literature, identify key themes, and synthesize findings to derive noteworthy insights.
• Critical appraisal: Critically evaluate the quality and validity of qualitative research and included studies by using BMC medical research methodology.
• Interpret and present your findings: Discuss the purpose and implications of your analysis, spotlighting key insights and limitations. Organize and present the findings coherently and systematically.

Structure of an Integrative Literature Review

• Introduction : Provide an overview of the research topic and the purpose of the integrative review.
• Methods: Describe the opted literature search strategy, selection criteria, and data extraction process.
• Results: Present the synthesized findings, including key themes, patterns, and contradictions.
• Discussion: Interpret the findings about the research question, emphasizing implications for theory, practice, and prospective research.
• Conclusion: Summarize the main findings, limitations, and contributions of the integrative review.

Pros and Cons of Integrative Literature Review

• Informs evidence-based practice and policy to the relevant stakeholders of the research.
• Contributes to theory development and methodological advancement, especially in the healthcare arena.
• Integrates diverse perspectives and findings
• Time-consuming process due to the extensive literature search and synthesis
• Requires advanced analytical and critical thinking skills
• Potential for bias in study selection and interpretation
• The quality of included studies may vary, affecting the validity of the review

Example of Integrative Literature Reviews

Paper Title: An Integrative Literature Review: The Dual Impact of Technological Tools on Health and Technostress Among Older Workers

5. Rapid Literature Review

A Rapid Literature Review (RLR) is the fastest type of literature review which makes use of a streamlined approach for synthesizing literature summaries, offering a quicker and more focused alternative to traditional systematic reviews. Despite employing identical research methods, it often simplifies or omits specific steps to expedite the process. It allows researchers to gain valuable insights into current research trends and identify key findings within a shorter timeframe, often ranging from a few days to a few weeks — unlike traditional literature reviews, which may take months or even years to complete.

When to Consider a Rapid Literature Review?

• When time impediments demand a swift summary of existing research
• For emerging topics where the latest literature requires quick evaluation
• To report pilot studies or preliminary research before embarking on a comprehensive systematic review

Steps to Conduct a Rapid Literature Review

• Define the research question or topic of interest. A well-defined question guides the search process and helps researchers focus on relevant studies.
• Determine key databases and sources of relevant literature to ensure comprehensive coverage.
• Develop literature search strategies using appropriate keywords and filters to fetch a pool of potential scientific articles.
• Screen search results based on predefined inclusion and exclusion criteria.
• Extract and summarize relevant information from the above-preferred studies.
• Synthesize findings to identify key themes, patterns, or gaps in the literature.
• Prepare a concise report or a summary of the RLR findings.

Structure of a Rapid Literature Review

An effective structure of an RLR typically includes the following sections:

• Introduction: Briefly introduce the research topic and objectives of the RLR.
• Methodology: Describe the search strategy, inclusion and exclusion criteria, and data extraction process.
• Results: Present a summary of the findings, including key themes or patterns identified.
• Discussion: Interpret the findings, discuss implications, and highlight any limitations or areas for further research
• Conclusion: Summarize the key findings and their implications for practice or future research

Pros and Cons of Rapid Literature Review

• RLRs can be completed quickly, authorizing timely decision-making
• RLRs are a cost-effective approach since they require fewer resources compared to traditional literature reviews
• Offers great accessibility as RLRs provide prompt access to synthesized evidence for stakeholders
• RLRs are flexible as they can be easily adapted for various research contexts and objectives
• RLR reports are limited and restricted, not as in-depth as systematic reviews, and do not provide comprehensive coverage of the literature compared to traditional reviews.
• Susceptible to bias because of the expedited nature of RLRs. It would increase the chance of overlooking relevant studies or biases in the selection process.
• Due to time constraints, RLR findings might not be robust enough as compared to systematic reviews.

Example of a Well-Executed Rapid Literature Review

Paper Title: What Is the Impact of ChatGPT on Education? A Rapid Review of the Literature

A Summary of Literature Review Types

Tools and Resources for Conducting Different Types of Literature Reviews

Online scientific databases.

Platforms such as SciSpace , PubMed , Scopus , Elsevier , and Web of Science provide access to a vast array of scholarly literature, facilitating the search and data retrieval process.

Reference management software

Tools like SciSpace Citation Generator , EndNote, Zotero , and Mendeley assist researchers in organizing, annotating, and citing relevant literature, streamlining the review process altogether.

Automate Literature Review with AI tools

Automate the literature review process by using tools like SciSpace literature review which helps you compare and contrast multiple papers all on one screen in an easy-to-read matrix format. You can effortlessly analyze and interpret the review findings tailored to your study. It also supports the review in 75+ languages, making it more manageable even for non-English speakers.

Goes without saying — literature review plays a pivotal role in academic research to identify the current trends and provide insights to pave the way for future research endeavors. Different types of literature review has their own strengths and limitations, making them suitable for different research designs and contexts. Whether conducting a narrative review, systematic review, scoping review, integrative review, or rapid literature review, researchers must cautiously consider the objectives, resources, and the nature of the research topic.

If you’re currently working on a literature review and still adopting a manual and traditional approach, switch to the automated AI literature review workspace and transform your traditional literature review into a rapid one by extracting all the latest and relevant data for your research!

There you go!

Frequently Asked Questions

Narrative reviews give a general overview of a topic based on the author's knowledge. They may lack clear criteria and can be biased. On the other hand, systematic reviews aim to answer specific research questions by following strict methods. They're thorough but time-consuming.

A systematic review collects and analyzes existing research to provide an overview of a topic, while a meta-analysis statistically combines data from multiple studies to draw conclusions about the overall effect of an intervention or relationship between variables.

A systematic review thoroughly analyzes existing research on a specific topic using strict methods. In contrast, a scoping review offers a broader overview of the literature without evaluating individual studies in depth.

A systematic review thoroughly examines existing research using a rigorous process, while a rapid review provides a quicker summary of evidence, often by simplifying some of the systematic review steps to meet shorter timelines.

A systematic review carefully examines many studies on a single topic using specific guidelines. Conversely, an integrative review blends various types of research to provide a more comprehensive understanding of the topic.

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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
• Data Extraction/Coding/Study characteristics/Results
• Reporting the quality/risk of bias
• Manage citations using RefWorks This link opens in a new window
• GW Box file storage for PDF's This link opens in a new window

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 :

Checklist for Artificial Intelligence in Medical Imaging (CLAIM). CLAIM is modeled after the STARD guideline and has been extended to address applications of AI in medical imaging that include classification, image reconstruction, text analysis, and workflow optimization. The elements described here should be viewed as a “best practice” to guide authors in presenting their research. Reported in Mongan, J., Moy, L., & Kahn, C. E., Jr (2020). Checklist for Artificial Intelligence in Medical Imaging (CLAIM): A Guide for Authors and Reviewers.  Radiology. Artificial intelligence ,  2 (2), e200029. https://doi.org/10.1148/ryai.2020200029

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.
• 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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Types of Literature Review

There are many types of literature review. The choice of a specific type depends on your research approach and design. The following types of literature review are the most popular in business studies:

Narrative literature review , also referred to as traditional literature review, critiques literature and summarizes the body of a literature. Narrative review also draws conclusions about the topic and identifies gaps or inconsistencies in a body of knowledge. You need to have a sufficiently focused research question to conduct a narrative literature review

Systematic literature review requires more rigorous and well-defined approach compared to most other types of literature review. Systematic literature review is comprehensive and details the timeframe within which the literature was selected. Systematic literature review can be divided into two categories: meta-analysis and meta-synthesis.

When you conduct meta-analysis you take findings from several studies on the same subject and analyze these using standardized statistical procedures. In meta-analysis patterns and relationships are detected and conclusions are drawn. Meta-analysis is associated with deductive research approach.

Meta-synthesis, on the other hand, is based on non-statistical techniques. This technique integrates, evaluates and interprets findings of multiple qualitative research studies. Meta-synthesis literature review is conducted usually when following inductive research approach.

Scoping literature review , as implied by its name is used to identify the scope or coverage of a body of literature on a given topic. It has been noted that “scoping reviews are useful for examining emerging evidence when it is still unclear what other, more specific questions can be posed and valuably addressed by a more precise systematic review.” [1] The main difference between systematic and scoping types of literature review is that, systematic literature review is conducted to find answer to more specific research questions, whereas scoping literature review is conducted to explore more general research question.

Argumentative literature review , as the name implies, examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. It should be noted that a potential for bias is a major shortcoming associated with argumentative literature review.

Integrative literature review reviews , critiques, and synthesizes secondary data about research topic in an integrated way such that new frameworks and perspectives on the topic are generated. If your research does not involve primary data collection and data analysis, then using integrative literature review will be your only option.

Theoretical literature review focuses on a pool of theory that has accumulated in regard to an issue, concept, theory, phenomena. Theoretical literature reviews play an instrumental role in establishing what theories already exist, the relationships between them, to what degree existing theories have been investigated, and to develop new hypotheses to be tested.

At the earlier parts of the literature review chapter, you need to specify the type of your literature review your chose and justify your choice. Your choice of a specific type of literature review should be based upon your research area, research problem and research methods.  Also, you can briefly discuss other most popular types of literature review mentioned above, to illustrate your awareness of them.

[1] Munn, A. et. al. (2018) “Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach” BMC Medical Research Methodology

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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 .

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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Aas 101: research methods for african american studies: writing a literature review.

• Finding Articles
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More useful information at this guide

• Conducting a Literature Review by Ann Glusker Last Updated Apr 25, 2024 1492 views this year

Literature review

A literature review surveys the scholarship on a particular topic, issue, or theory and provides a critical assessment of this literature.  The purpose of a literature review is to provide a written argument that supports the thesis by giving a succinct overview of previous research published on a topic. 

The Literature Review in four steps:

1. Identify the topic

• Usually based on research interest

2. Find important works of scholarship related to the topic

• seek advice from noted experts in the field
• search article database 
• search library catalogs
• review works cited pages - is there an author(s) consistently present

3. Evaluate and analyze the literature to determine which is most valuable to the topic

• preview(skim and scan), select, and organize the data

4. Write the review

For a more in-depth guide to writing a literature review, please refer to the following site

Learn How to Write a Review of Literature

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