On Registered Clinical Trials

A new PLoS ONE study looks at the effect of mandatory pre-registration of medical study methods and outcome measures, starting in 2000. Major findings:

• Studies finding positive effects fell from 57% prior to the registry to just 8% afterward.
• "...focused on human randomized controlled trials that were funded by the US National Heart, Lung, and Blood Institute (NHLBI) [and so required advanced registration by a 1997 U.S. law]. The authors conclude that registration of trials seemed to be the dominant driver of the drastic change in study results."
• "Steven Novella of Yale University in New Haven, Connecticut, called the study 'encouraging' but also 'a bit frightening' because it casts doubt on previous positive results...”
• "Many online observers applauded the evident power of registration and transparency, including Novella, who wrote on his blog that all research involving humans should be registered before any data are collected. However, he says, this means that at least half of older, published clinical trials could be false positives. 'Loose scientific methods are leading to a massive false positive bias in the literature,' he writes."

Reported in Nature here.