Skip to Main Content

Systematic Reviews & Expert Reviews

Types of Evidence

In the Health Sciences, we generally categorize evidence into two main types: Filtered and Unfiltered resources. When you look at the traditional evidence pyramid, we are looking at the research cycle: starting with unfiltered information (the original research), once a body of work is established, we can start analyzing and synthesizing the existing research, creating filtered information (i.e., systematic reviews and meta-analyses). This top-tier of evidence includes Systematic Reviews and other "expert reviews."

Image from

Expert Review Types


A systematic review uses systematic and explicit methods to identify, select, and critically appraise relevant research and to collect and analyze data from included studies.  It traditionally brings together evidence from the quantitative literature to answer questions on the effectiveness of a specific intervention for a particular condition.

  • Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.2 (updated February 2021). Cochrane, 2021. Available from



An integrative review critiques and synthesizes the literature on a topic in an integrated way to generate new frameworks or perspectives on the topic.  It allows for the inclusion of several study designs (e.g. experimental/nonexperimental, theoretical studies/empirical literature).  It is also known as a “comprehensive review” or a “critical overview.”



A scoping review maps the body of literature on a topic (often a broad topic) and identifies key concepts and research gaps.  It may include data from any type of evidence and research methodology.  It can be used as a standalone project or as a preliminary step to a systematic review.

  • Munn, Z., Peters, M., Stern, C., Tufanaru, C., McArthur, A., & Aromataris, E. (2018). Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC medical research methodology, 18(1), 143.
  • Arksey, H., & O’Malley, L. (2005). Scoping studies: towards a methodological framework. International Journal of Social Research Methodology, 8(1), 19–32.



A realist review looks to identify and explain social interventions or programs and the interactions between context, mechanisms, and outcomes for policy makers.  It seeks to answer the question, “What works, for whom, in what circumstances?”  It embraces multiple methods (both qualitative and quantitative).

  • Pawson, R., Greenhalgh, T., Harvey, G., & Walshe, K. (2005). Realist review—a new method of systematic review designed for complex policy interventions. Journal of Health Services Research & Policy, 10 Suppl1, 21–34.



An overview of reviews, or umbrella review, summarizes the evidence from multiple research syntheses into one accessible and usable document.  It is based on high-quality, reliable systematic reviews on a specific health problem or topic, and it explores the consistency of findings across reviews

  • Aromataris, E., et al. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. International Journal of Evidence-Based Healthcare, 13(3), 132–140.



Expert Methodologies and Review Types from Johns Hopkins University, CC BY-NC 4.0
Accessibility | Proxy Logout