LibGuides: Systematic Review Guide: Overview

What is a Systematic Review?

A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. By combining data, they improve the ability to study the consistency of results. Researchers conducting systematic reviews use explicit, systematic methods that are selected with a view aimed at minimizing bias, to produce more reliable findings to inform decision making and create reproducible research (Higgins et al., 2023). It is secondary research because secondary research does not involve generating data or talking to human subjects. It does not require IRB approval.

Because of the methodology of systematic reviews, they can take 12-24 months to complete.
Generally, two or more individuals independently review each article separately to determine whether it meets inclusion criteria. Cochrane will not publish a review that is proposed to be undertaken by a single person.
Reviews research literature using systematic and transparent methods, thereby making it reproducible.
Goal: Meant to help inform practice, creating clinical guidelines for patient care.

Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook.

When is a Systematic Review Appropriate?

Use the following flowchart adapted from Cornell Libraries to determine whether a systematic review is the appropriate study for your research question.

When is a systematic review not appropriate?

If your research question involves a relatively new topic or intervention, there may not be enough relevant, published evidence. In this case, consider a scoping or rapid review.
If you are working alone. Consider a literature review instead.
If you do not have sufficient time. Systematic reviews can take form 6-18 months to conduct. Those pressed for time may consider a rapid review.
If there are already published reviews on the topic. Make sure before embarking on any review, to always check databases for previously published work along with PROSPERO to see if there is already an ongoing registered study on the topic

Why are Systematic Reviews Important?

Given the comprehensive nature of systematic reviews, they are considered the top of the evidence-based pyramid.They are an important facet of research that helps with:

identifying gaps of knowledge in a field,
highlighting methodological concerns, specifically, bias risk, and
establishing which questions already provide clear answers given the available evidence.

Image: Andy Puro, 2014

Types of Reviews

Review Type	Description	Methodology
Systematic Review	Exhaustive and comprehensive search. Appraises and synthesizes research. Results of systematic reviews include what is known, recommendations for future research based on current research, what remains unknown, and any uncertainty during review. Example: Gamification and neurological motor rehabilitation in children and adolescents: a systematic review	Cochrane Handbook for Systematic Reviews of Interventions
Meta-Analysis	Statistically combines the outcomes of quantitative studies to measure the effect of the results of a similar issue. Exhaustive and comprehensive search. Example: Respiratory syncytial virus hospitalization and mortality: Systematic review and meta-analysis	Cochrane Handbook for Systematic Reviews of Interventions: Chapter 10
Network Meta-Analysis	Similar to a meta-analysis, except it is used to compare three or more interventions simultaneously in a single analysis by combining both direct and indirect evidence across a network of studies. Example: Real-world evidence comparing oral anticoagulants in non-valvular atrial fibrillation: a systematic review and network meta-analysis	Cochrane Handbook for Systematic Reviews of Interventions:Chapter 11
Rapid Review	More time-sensitive than other review types. Typically takes 1-6 months to complete. Analyzes the quantities of literature and general direction of results. Less rigorous compared to other review types with limited interpretation of findings. Example: Risk factors for severity of COVID-19: a rapid review to inform vaccine prioritisation in Canada	Cochrane Rapid Reviews: Interim Guidance
Mixed Methods (Integrative) Review	When a combination of methods (such as qualitative and quantitative) are used to review an intervention. This method combines the findings of both types of reviews in order to identify research gaps. Typically take 12-18 months to complete. Example: General practitioners' knowledge, attitudes, beliefs and practices surrounding the prescription of e-cigarettes for smoking cessation: a mixed-methods systematic review	JBI Manual for Evidence Synthesis: Chapter 8
Umbrella Review	Compilation of evidence from many reviews and highlights interventions. Assesses quality of reviews and provides recommendations, lists what remains unknown, as well as recommendations for future research. Example: Risk factors for endometrial cancer: An umbrella review of the literature	JBI Manual for Evidence Synthesis: Chapter 9
Literature Review	A traditional literature review is typically narrative in nature and used to justify the need for one's planned research by covering a wide range of subjects at various levels of completeness and comprehensiveness. They are more likely to contain bias. Example: A Literature Review of Real-World Effectiveness and Safety of Dupilumab for Atopic Dermatitis	Ten Simple Rules for Writing a Literature Review
Scoping Review	Scoping reviews are primarily used to identify exploratory and novel concepts. Usually, the research question or topic is broad and the sources of evidence are heterogeneous in nature thereby investigating many approaches. Example: Barriers and facilitators to perioperative smoking cessation: A scoping review	JBI Manual for Evidence Synthesis: Chapter 10

Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J. 2009 Jun;26(2):91-108. PMID: 19490148.

Attribution

In addition to credit given for various images, parts of this guide were adapted from work/guides by:

Louisiana State University, Cornell University

Used with permission or in accordance with Creative Commons Licensing.

Systematic Review Guide