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Systematic Reviews in Health

What are Systematic Reviews?

A systematic review is a review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the included studies. Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies. Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies.1

Systematic reviews differ from traditional narrative reviews and the key characteristics of a systematic review are:

  • a clearly stated set of objectives with pre-defined eligibility criteria for studies;
  • an explicit, reproducible methodology;
  • a systematic search that attempts to identify all studies that would meet the eligibility criteria;
  • an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
  • a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

The Need for Systematic Reviews

Systematic reviews are the "gold standard" for synthesizing evidence in health because of their rigorous methodology.  They are an important source of evidence to guide the development of clinical practice guidelines and to inform clinical decision-making.  The first three steps in the Evidence-Based Practice (EBP) process are covered by the process of completing a systematic review - Ask, Acquire, Appraise:

5 steps of evidence-based practice

Practitioners (decision-makers) can therefore use systematic reviews to cover the first three steps of the EBP process and then focus their efforts on the subsequent steps of Apply and Audit.2 More generally systematic reviews provide healthcare professionals, consumers, researchers, and policy makers with identified, appraised, and synthesized research-based evidence in an accessible format, therefore saving them considerable time.3

Due to their comprehensive methodology, systematic reviews sit at the top of the research evidence hierarchy.

Evidence hierarchy


1. Higgins, P.T., & Green, S. (eds.). (2008). Cochrane handbook for systematic reviews of interventions.  Chichester, England ; Hoboken, NJ : Wiley- Blackwell.  Available:

2. O'Connor, E., Whitlock, E., & Spring, B. (2007). Introduction to systematic reviews. Available:

3. Mulrow, C.D. (1994). Rationale for systematic reviews. BMJ 309: 597-599. Available: