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Systematic Review?? But first, Evidence Synthesis.
To describe what a Systematic Review is, we must first define Evidence Synthesis.
Evidence synthesis (ES) involves combining information from multiple studies investigating the same topic to comprehensively understand their findings. This helps determine:
- How effective a particular treatment or drug is
- How people have experienced a particular health condition or treatment
By using ES effectively, policymakers, healthcare institutions, clinicians, researchers, and the public can make more informed decisions about health and healthcare.
This 3-minute video from from Cochrane explains ES and why we need it:
What is a Systematic Review?
A Systematic Review (SR) is a form of ES...
...that uses a specific methodology that aims to comprehensively identify all relevant studies on a specific topic. Furthermore, appropriate studies are selected based on explicit criteria. Systematic Reviews aim to be transparent, verifiable, and reproducible, which lends itself to the likelihood of considerably smaller research bias.
Although the SR methodology was originally developed in the field of medicine, its value is evident in nursing, education, policing, criminology, public policy, and management.
Other types of reviews: Click on each tab to learn more...
Generic term for the most basic form of ES. Includes published materials that provide examination of recent or current literature. These can cover wide range of subjects at various levels of completeness and comprehensiveness and may include research findings.
Search: May or may not include comprehensive searching
Appraisal: May or may not include quality assessment
Synthesis: Typically narrative
Analysis: Analysis may be chronological, conceptual, thematic, etc.
Preliminary assessment of potential size and scope of available research literature, these aim to identify the nature and extent of research evidence (usually including ongoing research).
Search: Completeness of searching determined by time & scope constraints
Appraisal: No formal quality assessment
Synthesis: Typically tabular with some narrative commentary
Analysis: Characterizes quantity and quality of literature, perhaps by study design and other key features
Technique that statistically combines the results of quantitative studies to provide a more precise effect of the results.
Search: Aims for exhaustive, comprehensive searching that may use a funnel plot to assess completeness
Appraisal: Quality assessment may determine inclusion / exclusion and / or sensitivity analyses
Synthesis: Graphical and tabular with narrative commentary
Analysis: Numerical analysis of measures of effect assuming absence of heterogeneity
Tends to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research.
Search: Aims for comprehensive searching of current literature
Appraisal: No formal quality assessment
Synthesis: Typically narrative, but may have tabular accompaniment
Analysis: Current state of knowledge and priorities for future investigation and research
Assessment of what is already known about a policy or practice issue, by using SR methods to search and critically appraise existing research
Search: Completeness of searching determined by time constraints
Appraisal: Time-limited formal quality assessment
Synthesis: Typically narrative and tabular
Analysis: Quantities of literature and overall quality / direction of effect of literature
The review types included in this research guide represent just a few that have been identified in the literature. In 2019, researchers identified 48 types of reviews and categorized them into seven families! Therefore, it could be easy to get overwhelmed with review project formats. But remember, you don't have to - we can help!
References
Cochrane Ireland. (2023, May 4). Evidence Synthesis—What is it and why do we need it? Cochrane. https://www.cochrane.org/news/evidence-synthesis-what-it-and-why-do-we-need-it
CEBMa. (n.d.). What is a Systematic Review (SR)? Retrieved May 27, 2025, from https://cebma.org/resources/frequently-asked-questions/what-is-a-systematic-review/
Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies: A typology of reviews, Maria J. Grant & Andrew Booth. Health Information & Libraries Journal, 26(2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x
Acknowledgement: This guide design was adapted from UNC Health Science Library Systematic Reviews LibGuide © 2025 by Emily P. Jones is licensed under CC BY-NC 4.0. https://guides.lib.unc.edu/systematic-reviews