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Understanding Review Types

Systematic Reviews and Meta-Analyses

A systematic review or meta-analysis is a study of studies. These reviews aim to collect all existing evidence to address a specific research question. The criteria used to select included evidence is pre-defined and responds precisely to the research question. Explicit methods to minimize bias and increase transparency are used to produce a reliable synthesis of information. The purpose of this synthesized information is to create strong evidence to inform clinical decision-making, policy and research.

  Systematic review without meta-analysis Systematic Review with meta-analysis
METHOD Systematically search for, appraise, and synthesize research evidence from the studies identified Synthesis includes use of statistical techniques to combine data from the studies identified
FORMAT Results are typically narrative, may have tabular component Results are graphical and tabular with narrative commentary
CONTENT Analyzes what is known; recommendations for practice. Identifies what remains unknown; uncertainty around findings, recommendations for future research Includes numerical determination of effect size and variance


All meta-analyses are systematic reviews, but not all systematic reviews are meta-analyses. There are six steps to consider:

  1. Plan – Frame research question, determine inclusion and exclusion criteria for studies, create project management outline including deadlines and responsibilities, and develop protocol
  2. Identify – Determine search terms and databases to search, retrieve studies, and document findings
  3. Evaluate – Screen, select, sort, and appraise studies
  4. Collect & Code – Develop forms, code selected studies, and synthesize data extracted
  5. Explain – Analyze findings and put them into context
  6. Summarize – Write up the report

These steps usually take about 12 months. Systematic reviews and meta-analyses are undertaken by a research team rather than individual researchers to facilitate expedited review of studies and reduce researcher bias.

Librarians are involved most heavily with step two: the “Identify” step, where expert search skills play a crucial role. Searching is a critical part of conducting systematic reviews and errors made in the search process can result in biased or incomplete evidence. Researchers seeking help with systematic reviews can help their librarians by having a general sense of the literature in the field, including knowledge of key works and specialized terminology.


Grant, M. & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologiesHealth Information and Libraries Journal, 26(2), 91-108. DOI: 10.1111/j.1471-1842.2009.00848.x

Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 6 [updated Sept 2018]. The Cochrane Collaboration, 2018. Available from