ABSTRACT
Contemporary medical practice is strongly infl uenced by the idea that clinical decision-making should be based on the results of clinical trials. A number of interrelated trends, stretching back several decades, have converged on a view of what counts as good medical research. This chapter begins with a brief history of three connected movements-clinical epidemiology, evidence-based medicine (EBM), and the Cochrane Collaboration-which aim to promote the use of high-quality evidence from clinical research in patient care. “High-quality evidence” is usually understood as evidence at the top of a “hierarchy of evidence,” specifi cally randomized controlled trials (see Chapter 18 ) and systematic reviews or meta-analyses of such studies. The remainder of the chapter will discuss these ideas in detail, examining both the arguments for and the criticisms of hierarchical rankings of study methods, and of the combination of research results in a meta-analysis.
