Systematic reviews in emergency medicine: Part I. Background and general principles for locating and critically appraising reviews.

Reviews of the medical literature have always been an important resource for physicians. Increasingly, qualitative and quantitative "systematic reviews" have replaced the traditional "narrative review" as a means of capturing and summarizing current evidence on a topic or, when possible, answering a specific clinical question. This paper is part one of a two-part series designed to provide emergency physicians with the background necessary to locate, critically evaluate and interpret systematic reviews. The paper provides a brief background on systematic reviews and general principles on locating and critically appraising them. To facilitate readability, examples from the emergency medicine literature have been included for illustrative purposes and technical details have been kept to a minimum. The references, however, are comprehensive and provide a resource for readers seeking further information.