Misunderstandings, misperceptions, and mistakes.

iscussions about evidence-based medicine (EBM) have engendered both positive and negative reactions from clini-cians, researchers, and policymakers since the term was first coined in the early 1990s (1, 2). These discussions were brought to the forefront again in a recent commentary by Dr. Bernadine Healy, former Director of National Institutes of Health (NIH), in US News and World Report(3). She raised several issues that practitioners and teachers of EBM face when advocating this model of care. First, she stated that EBM practitioners advocate using the " best " evidence, which is mostly taken from randomized trials and cost-benefit studies. Second, she raised the issues of the interpretation of evidence for screening mammography and prostate specific antigen (PSA) as examples where EBM has failed because EBM proponents did not advocate for these tests based on the available evidence. Third, she likened the practice of EBM to a " straitjacket " or a cookbook approach in which both clinician judgement and patient values and circumstances are ignored. All of these criticisms of EBM stem from misperceptions or misunderstandings and can be answered by careful consideration of the definition of EBM. EBM is defined as the integration of the best available evidence with our clinical expertise and our patient's unique values and circumstances (4). Evidence, whether strong or weak, is never sufficient to make clinical decisions. Individual values and preferences must balance this evidence to achieve optimal shared decision making. Others besides Dr. Healy have stated their concern that only randomized trials or systematic reviews constitute the evidence in EBM (5, 6). Proponents of EBM would acknowledge that several sources of evidence inform clinical decision making. The practice of EBM stresses finding the best available evidence to answer a question and this evidence may come from randomized trials, rigorous observational studies or even anecdotal reports from experts. Hierarchies of evidence have been developed to help describe the quality of evidence that may be found to answer clinical questions. Randomized trials and systematic reviews of randomized trials provide the highest quality evidence – that is, the lowest likelihood of bias, and thus the lowest likelihood of misleading for establishing the effect of an intervention, but they are not usually the best sources for answering questions about diagnosis, prognosis, or the harmful impact of potentially noxious exposures. Although this hierarchy has been criticized for devaluing the basic sciences (6), we suggest that numerous studies have …