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PT 8500: Systematic Review and Meta-Analysis in the Health Sciences: What's a Systematic Review?

A research guide for Dr. Gordon Warren's class.

What IS a Systematic Review?

A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question.  It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made. 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.

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 https://training.cochrane.org/handbook


How is a Meta-Analysis Different from a Systematic Review?

DEFINITION 1:  Many systematic reviews contain meta-analyses. Meta-analysis is the use of statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analyses can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review (see Chapter 9, Section 9.1.3). They also facilitate investigations of the consistency of evidence across studies, and the exploration of differences across studies.

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 https://training.cochrane.org/handbook

 

DEFINITION 2:  A systematic review is an overview of primary studies that used explicit and reproducible methods.  A meta-analysis is a mathematical synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way.  Although meta-analysis can increase the precision of a result, it is important to ensure that the methods used for the review were valid and reliable.

Trisha Greenhalgh.  How to read a paper: Papers that summarise other papers (systematic reviews and meta-analyses) BMJ 1997; 315: 672. Available here.