How to select a review type
There are many types of evidence synthesis. Selecting the right approach for your project is an important early consideration for your team. The type of review you select is influenced by your research question, as well as the outcomes you hope to achieve.
In Sutton et al., the Results section details an extensive list of review types and their definitions. What follows are our abbreviated descriptions of some of the most common review types you will encounter.
Stumped? Still wondering what review type to select? Try the quiz tool Right Review.
Systematic Review & Meta-Analysis
Systematic Review
Systematic reviews use explicit, systematic methods to collate and synthesize findings of studies that address a clearly formulated question. Systematic reviews aim to use comprehensive and exhaustive searching to identify and gather all relevant articles. Once all relevant articles are selected, a review team assesses and synthesizes the quality of the research. The results of this work are represented in the systematic review with a narrative of the findings, as well as visual graphs or charts to capture impact. There are defined processes and procedures to adhere to when conducting a systematic review. The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) reporting guidelines include a checklist, which addresses what information should be included in a systematic review or meta-analysis.
Meta-Analysis
Sometimes a meta-analysis is bundled with a systematic review. A meta-analysis can provide a standardized approach by helping to determine the effect of a treatment or exposure; this is accomplished by combining statistical results from two or more studies, which is represented on a forest plot.
Figure: Chlorfenapyr-pyrethroid ITNs versus pyrethroid-only ITNs: Parasite prevalence (12-months). https://doi.org/10.1371/journal.pone.0289469.g007
Why don't all systematic reviews include meta-analysis?
Meta-analysis can improve the precision of an effect estimate, but it can also be misleading if it is performed with data that are not sufficiently similar or with data whose methodological quality is poor (e.g. the study participants were not properly randomized). It's not always appropriate to use a meta-analysis, which is why many systematic reviews do not include them. Systematic reviews can still synthesize study data in other ways to represent outcomes.
Examples of Systematic Reviews & Meta-Analyses
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Scoping Review
A scoping review is a useful methodology when the purpose of the review is to:
- Identify knowledge gaps
- Scope a body of literature
- Clarify concepts
- Investigate research conduct
Scoping reviews can also serve as precursors to systematic reviews and can be used to confirm the relevance of inclusion criteria and potential questions. Although the purpose for completing scoping and systematic reviews differs, both processes require rigorous and transparent methods to ensure results are unbiased.
Scoping reviews have their own reporting guidelines, PRISMA extension. This is a document with guidance for how they should be conducted.
Scoping Review or Systematic Review...Decisions, Decisions!
Unsure if a scoping or a systematic review is most appropriate for your research interest? Check out Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach.
Example of a Scoping Review
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Umbrella Review
This could be described as a 'review of reviews' because they are designed to synthesize evidence from other published systematic reviews and/or meta-analyses on a broad topic. When multiple systematic reviews are published in the same year, it can be difficult to assess the outcomes in order to identify and apply the best evidence; umbrella reviews facilitate the gathering and assessment of multiple systematic reviews and meta-analyses.
Figure: chart of synthesized findings from an umbrella review. https://jbi-global-wiki.refined.site/space/MANUAL/355830364/9.3.9+Summary+of+Evidence
Example of an Umbrella Review
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Rapid Review
Rapid reviews use modified systematic review methods to accelerate the review process while maintaining systematic, transparent, and reproducible methods; this includes abbreviating or limiting the literature search in some way to accelerate review production. A rapid review should never be selected if the goal is to reduce the amount of time it takes to complete an evidence synthesis project.