The promise and pitfalls of systematic reviews.

The systematic review "movement" that has transformed medical journal reports of clinical trials and reviews of clinical trials has taken hold in public health, with the most recent milestone, the publication of the first edition of The Guide to Community Health Services in 2005. In this paper we define and distinguish current terms, point out important resources for systematic reviews, describe the impact of systematic review on the quality of primary studies and summaries of the evidence, and provide perspectives on the promise of systematic reviews for shaping the agenda for public health research. Several pitfalls are discussed, including a false sense of rigor implied by the terms "systematic review" and "meta-analysis" and substantial variation in the validity of claims that a particular intervention is "evidence based," and the difficulty of translating conclusions from systematic reviews into public health advocacy and practice.