Randomized clinical trials: the meeting place of medical practice and clinical research.

Randomized clinical trials (RCTs) have been used to assess interventions affecting health since biblical times. They provide the most valid means of measuring the true effects of intervention compared with no treatment or placebo. Although they can also be used to assess the value of diagnostic tests, this article focuses on randomized trials in the context of treatment. Key elements of an RCT include: the explicit definition of a clinically relevant question; the identification of an appropriate sample of patients; a clearly defined and reproducible intervention; an appropriate intervention and comparator; clinically relevant, measurable outcomes; and appropriate tools for measurement and analysis. It is also essential to establish that the question posed is ethical, the methods of study are valid, and that follow-up is complete, with an "intent to treat" analysis. Results are best presented using both proportions and absolute numbers. By providing clinical decision-makers with numbers needed to treat or harm, decisions may be better informed and easier to understand, than if proportions alone are used.