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-reivew_wordledefined and responds precisely to the research question. Explicit methods to minimize bias and increase transparency are used to produce 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 Meta-analysis
METHOD Systematically search for, appraise, and synthesize research evidence Statistically combine the results of quantitative studies to provide a more precise effect of the results
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 Numerical analysis of measure of effect assuming absence of heterogeneity.

It is important to note that 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 – Determine 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 takes about 12 months, with a minimum of 6 months recommended. 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.

UMLHSL_Logo_col_horzontalLibrarians 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 (see our previous post on literature reviews), including knowledge of key works and specialized terminology. For more information about systematic reviews, see our Systematic Review Search LibGuide.

When in doubt, email or book an appointment with one of our librarians! http://lib-umanitoba.libcal.com/appointments/

This article is a part of the HSL News series Understanding review types. For more information about this series, read the series’ introduction.

References

Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from http://handbook.cochrane.org/

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

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