Applying overviews and meta-analyses at the bedside

Abstract

In 1960, the randomized clinical trial was an oddity. It is now accepted that virtually no drug can enter clinical practice without a demonstration of its efficacy in clinical trials. Moreover, the same randomized trial method increasingly is being applied to surgical therapies [l], and diagnostic tests [2]. Meta-analysis is gaining increasing acceptance as a method of summarizing the results of a number of randomized trials, and ultimately may have as profound an effect on setting treatment policy as have randomized trials themselves [3]. While less dramatic, crucial methodolgical advances have also been made in other areas, such as the assessment of diagnostic tests and prognoses [4, 51. A new philosophy of medical practice and teaching has followed these methodological advances. This shift is manifested in a number of ways. There has been a profusion of articles instructing clinicians on how to access [6], evaluate [7], and interpret [8] the medical literature. The Journal of the American Medical Association has begun a new, continuing series of articles on the precision and accuracy of the clinical examination [9, lo]. Proposals to apply the principles of clinical epidemiology to day-today clinical practice have been put forward [ 111, and clinical clerks, house officers, and faculty are preparing one-page “critically-appraised topics” summaries (“CATS”) of approaches to diagnosis, prognosis, and therapy [12]. A number of major medical journals have adopted a more informative structured abstract format which incorporates issues of methods and design into the portion of an article the reader sees first [13]. The American College of Physicians has launched a journal, ACP Journal Club, that summarizes new publications of high relevance and methodologic rigour [14], and plans are under way for a similar but expanded publication with the tentative title: Journal of Evidence-based Medicine. Textbooks which provide a rigorous review of available evidence, including a methods section describing both the methodologic criteria used to systematically evaluate the validity of the clinical evidence and the quantitative techniques used for summarizing the evidence, have begun to appear [15, 161. Practice guidelines based on rigorous methodological review of the available evidence are increasingly common [17]. A final manifestation is the growing demand for courses and seminars which instruct physicians on how to make more effective use of the medical literature in their day-to-day patient care. We call the new approach “evidence-based medicine” [18] when applied by individual clinicians to individual patients, and “evidencebased health care” when applied by public health professionals, administrators, and policymakers to groups of patients and populations. The traditional approach was based on the following assumptions about the knowledge required to guide clinical practice.