What are systematic reviews?
Systematic reviews differ from traditional narrative expert-opinion reviews in their comprehensive systematic approach to summarizing health-care evidence (Levin, 2001) and are now required by some biomedical journals (for example, The Lancet) for clinical trial publication (Young and Horton, 2005). The systematic approach starts with formulation of a clear question, followed by a thorough search for all relevant evidence, a critical appraisal of that evidence using predetermined criteria, quantitative pooling (metaanalysis) of similar study results when appropriate, and finally, interpretation of that evidence (Bigby et al., 2003). Authors of systematic reviews conducted within the Cochrane Collaboration make a commitment to update the review periodically with the goal of fine-tuning the research in light of any new studies that come along. If performed correctly, these reviews can provide complete, up-to-date, and unbiased measurements of treatment effectiveness by using metaanalytic
