Randomized clinical trials: how long should they last?

Well-conducted randomized clinical trials (RCT) are essential for the objective assessment of the value of new diagnostic or therapeutic medical interventions. They also will give us information about the effect of the intervention on cost and quality of life. Although the RCT was introduced 50 years ago, the requirements to ensure the best possible quality are continuously scrutinized.1–4 That holds for several aspects of the RCT, such as the proper selection of patients, fulfilling strict criteria to make groups comparable, correct calculation of the required number of patients, well-defined end points, adequate information and follow-up care of the patients, and clarity about medicolegal aspects. An important issue in the RCT is the required length of the study to come to a meaningful outcome.