Randomized clinical trials (RCTs) are the gold standard for advancing the science of medicine. However, many important clinical questions probably will never be answered by RCTs simply because many trials are extraordinarily expensive and RCTs might not always be appropriate for addressing some research questions. In fact, most clinical trials do not enroll typical patients; trial participants are volunteers who agree to be studied with limited compensation and often do so primarily to benefit other patients. Clinical trials are designed to answer questions about whether something works (efficacy), but usually are poorly suited to answer questions about how well something works on usual patients seen in clinical practice (effectiveness). Numerous studies have shown that the effect sizes reported in clinical trials are rarely achieved in practice, raising concerns that more generalizable results are needed to better inform real-world clinical decisions.1-5
Safford MM. Comparative Effectiveness Research and Outcomes of Diabetes Treatment. JAMA. 2014;311(22):2275–2276. doi:10.1001/jama.2014.4313
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