Understanding Literature Reviews in Healthcare: Systematic Reviews

All types of literature reviews in this series are systematic reviews in that they are all done systematically, but only one kind of review is given the label systematic review.

This is the second article in the Understanding Literature Reviews in Healthcare series. The first article discussed narrative reviews.

Systematic Reviews

A systematic review is a thorough, method-driven exploration of a research question aimed at eliminating bias and delivering the most reliable answers to a specific question. Adhering to a structured process for collecting, evaluating, and synthesizing all relevant studies provides a clear, evidence-based foundation for decision-making in evidence-based practice.¹

Systematic reviews are not for the faint of heart. Booth estimates most systematic reviews of quantitative evidence take 12-18 months to complete.² By its very nature, a single person cannot complete a systematic review. For proper screening of studies, at least three reviewers are needed, but most teams include more than three members.¹

Pros and Cons

Pros of Systematic Reviews

•  High-Quality Evidence: Employs rigorous methods to reduce bias
• Comprehensive & Reproducible: Adheres to a structured and transparent process
• Supports Evidence-Based Practice: Aids in guiding policy and clinical decisions
• Identifies Research Gaps: Points out areas requiring further study
• Includes Statistical Analysis: Frequently incorporates meta-analysis for more robust conclusions^1,3

Cons of Systematic Reviews

• Time-Consuming: Can take months or even years to complete
• Resource-Intensive: Requires access to databases, software, and expertise
• Limited by Available Studies: Quality depends on the existing body of research 
• May Become Quickly Outdated: New studies can change findings over time 
• Can Be Too Narrow: Strict inclusion criteria might exclude valuable contributions^1,3

Methodology/Guidelines

Methodology

Several organizations have developed methodologies for systematic reviews. I am most familiar with the Cochrane Collaboration and JBI (formerly known as the Joanna Briggs Institute).

• JBI Manual for Evidence Synthesis: A comprehensive guide for authors conducting systematic and scoping reviews using JBI methodologies, with each chapter dedicated to synthesizing different types of evidence to address various clinical and policy-related questions
• Cochrane Handbook for Systematic Reviews of Interventions: The official guide outlining the preparation and maintenance of Cochrane systematic reviews on healthcare interventions addresses standard methods such as planning, searching, data collection, risk of bias assessment, and statistical analysis, along with specialized topics like non-randomized studies and complex interventions
• Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy
• Cochrane-Campbell Handbook for Qualitative Evidence Synthesis

Duke University’s Medical Center Library and Archives lists additional systematic review manuals.

Protocols

Before beginning your systematic review, you will need to register a protocol. A systematic review protocol is a pre-study plan that outlines the objectives, methods, and criteria for a systematic review. By detailing these elements in advance, the protocol improves transparency, minimizes bias, and streamlines the review process, ultimately saving time and resources.⁴

• A Practical Guide: Protocol Development for Systematic Reviews: This helpful guide from Covidence walks your team through each step of writing and registering your systematic review and meta-analysis protocol.
• Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P): This checklist highlights 17 key items that are important for creating protocols for systematic reviews and meta-analyses; designed to support your team in developing a thorough and well-rounded protocol
• PRISMA-P 2015: Elaboration and Explanation: Shares a detailed overview of each item on the PRISMA-P checklist

Reporting Guidelines

By now, you probably recognize that systematic procedures are a hallmark of systematic reviews. This structured approach also involves documenting all steps taken during the review process. Many journals require the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist for all systematic review submissions. Since the development of the original PRISMA statement, extensions have been created for other types of publications, including PRISMA-P, a PRISMA extension for protocols.

• PRISMA 2020 Explanation and Elaboration: This paper outlines the process for completing a PRISMA checklist and provides examples
• PRISMA for Searching (PRISMA-S): Although not mandatory for submission, the PRISMA-S guarantees that searching strategies are documented in sufficient detail to allow reproducibility
• Enhancing the QUAlity and Transparency Of health Research (EQUATOR) Network: The EQUATOR Network Library “contains a comprehensive searchable database of reporting guidelines and also links to other resources relevant to research reporting” beyond systematic reviews

Assessment

Systematic reviews are intended to minimize bias and offer high-quality evidence. However, simply labeling a review as “systematic” does not ensure its quality. Before relying on a systematic review for healthcare decisions, it’s crucial to assess both the quality of the review and the evidence it presents. To aid in this process, an international group of skilled systematic review authors created AMSTAR (A MeaSurement Tool to Assess systematic Reviews) 2, a tool designed for the evaluation of systematic reviews.

Systematic Review Examples

How do these systematic reviews rate on the AMSTAR 2 checklist?

• Antonio-Santos A, Vedula SS, Hatt SR, Powell C. Occlusion for stimulus deprivation amblyopia. Cochrane Database Syst Rev. 2020 Mar 23;3(3):CD005136. doi: 10.1002/14651858.CD005136.pub4. PMID: 32203629; PMCID: PMC7089638.
• Gorenshtein A, Liba T, Leibovitch L, Stern S, Stern Y. Intervention modalities for brain fog caused by long-COVID: systematic review of the literature. Neurol Sci. 2024 Jul;45(7):2951-2968. doi: 10.1007/s10072-024-07566-w. Epub 2024 May 2. PMID: 38695969; PMCID: PMC11176231.

Learn More

If you want to dive deeper into systematic reviews, here are some great resources.

• This workbook from the University of North Carolina at Chapel Hill Health Sciences Library guides you through the complete systematic review process, from assembling a team to writing the review. A video series and an online guide supplement the workbook.
• Systematic Approaches to a Successful Literature Review* by Booth, Sutton, Clowes, and Martyn-St James (3rd edition) is an excellent resource for any literature review. You don’t need to buy the book to access the free online resources. If you lack the funds for the latest edition, Booth offers free access to the 2nd edition.
• Foster and Jewell created the PIECCESS framework for librarians and information professionals. I highly recommend their book, Piecing Together Systematic Reviews and Other Evidence Syntheses: A Guide for Librarians.* I find this book so helpful that I own a print version and the ebook. Additionally, you can learn more about the framework from the five-part video series Piecing Together Systematic Reviews.

*I earn a small commission from products purchased using my affiliate links.

This brief list of resources only hints at the abundance available. Don’t hesitate to ask your librarian for further assistance; they can link you to many more resources that you can access. What systematic resources have you found helpful? Share your thoughts in the comments.

Final Thoughts

Many view systematic reviews as the gold standard for synthesizing evidence, influencing everything from clinical decisions to policy-making. Although they demand time, expertise, and rigorous methodology, their ability to minimize bias and provide reliable insights is invaluable.

If you’re starting your first systematic review, utilize the many guides, protocols, and frameworks available—and don’t hesitate to collaborate with experts in the field.

Next up: Meta-analysis

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References

1. Cumpston M, Flemyng E, Thomas J, Higgins J, Deeks J, Clarke M. Chapter I: Introduction. In: Higgins J, Thomas J, Chandler J, Cumpston M, Li T, Page M, et al., editors. Cochrane Handbook for Systematic Reviews of Interventions [Internet]. 6.5. Cochrane; 2024 [cited 2025 Mar 15]. Available from: https://training.cochrane.org/handbook/current/chapter-i
2. Booth A. EVIDENT Guidance for Reviewing the Evidence: a compendium of methodological literature and websites. 2016.
3. Maggio LA, Samuel A, Stellrecht E. Systematic Reviews in Medical Education. J Grad Med Educ. 2022 Apr 14;14(2):171–5.
4. Shamseer L, Moher D, Clarke M, Ghersi D, Liberati A, Petticrew M, et al. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015: elaboration and explanation. BMJ. 2015 Jan 2;349:g7647.