Critically appraising qualitative research for systematic reviews: defusing the methodological cluster bombs.

This article examines the place of qualitative research within systematic reviews as evidence for policy, discusses the critical appraisal process as applied to qualitative research, and gives illustrative examples of sound qualitative studies from the health policy field. A checklist is a useful tool for the quality evaluation of qualitative research, facilitating comparison of the strengths and weaknesses of different studies, and should stimulate debate between reviewers as part of the broader critical appraisal process. Critical appraisal must be central to research syntheses, thus enabling reviewers to make only good-quality qualitative evidence accessible for policy makers and practitioners.