Deciding how much confidence to place in a systematic review

by Simon Lewin, Andrew D Oxman, John N Lavis, Atle Fretheim | Dec 16, 2009

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The reliability of systematic reviews of the effects of health interventions is variable. Consequently, policymakers and others need to assess how much confidence can be placed in such evidence. The use of systematic and transparent processes to determine such decisions can help to prevent the introduction of errors and bias in these judgements.

In this article, we suggest five questions that can be considered when deciding how much confidence to place in the findings of a systematic review of the effects of an intervention. These are:

  1. Did the review explicitly address an appropriate policy or management question?
  2. Were appropriate criteria used when considering studies for the review?
  3. Was the search for relevant studies detailed and reasonably comprehensive?
  4. Were assessments of the studies' relevance to the review topic and of their risk of bias reproducible?
  5. Were the results similar from study to study?