Effectiveness and Comparative Effectiveness Reviews, systematic reviews of existing research on the effectiveness, comparative effectiveness, and comparative harms of different medical tests, are intended to provide relevant evidence to inform real-world health care decisions for patients, providers, and policymakers. In an effort to improve the transparency, consistency, and scientific rigor of the work of the Effective Health Care (EHC) Program, the Agency for Healthcare Research and Quality (AHRQ), the Scientific Resource Center, and the Evidence-based Practice Centers (EPCs), have developed this (also referred to as the . We intend it to serve as a resource for the EPCs as well as for other investigators interested in conducting systematic reviews on medical tests. We hope it will be a practical guide both for those who prepare the systematic reviews and those who use them in clinical practice, research development, and in making policy decisions.