Abstract
Systematic reviews are increasingly common as a means of assessing the relative effectiveness of health care interventions. This is not least because of the formation of the Cochrane Collaboration with its aim to prepare, maintain and promote the accessibility of reviews in all areas of health care.1 Just as systematic reviews contribute to the practice of evidence-based health care, so should the conduct of reviews be based on good evidence, ideally from empirical research. The paper by Juni et al.2 adds to this evidence base.