Monitoring clinical trials—interim data should be publicly available

Interim results from clinical trials are, by growing convention, scrutinised by committees, commonly called data monitoring committees or institutional review boards. This allows clear evidence of benefit or harm to be identified expeditiously. The UK Medical Research Council sponsored trial of folic acid prophylaxis against recurrence of neural tube defects1 and a trial of antiarrhythmic medication for prophylaxis against ventricular fibrillation2 were terminated early because of favourable and adverse interim results respectively. Current practice is to keep interim data secret, on the presumption that their release would undermine recruitment and provoke “premature” adoption of treatment. Data monitoring committees offer timely expert advice on such matters as data collection 3 4 and can stop patients being offered randomisation to treatments that would be regarded as inferior by almost any person who had understood the interim data. Knowledge accrues incrementally,5 however, and we argue that interim results should be made publicly available, thereby enabling patients to make individual decisions on the basis of data that might rationally provoke different choices from different people. Firstly, we explain why the practice of withholding data is ethically dubious, and, secondly, we argue that making data publicly available has potential practical advantages.