Registered clinical trials make positive findings vanish : Nature News & Comment

"The launch of the clinicaltrials.gov registry in 2000 seems to have had a striking impact on reported trial results, according to a PLoS ONE study1 that many researchers have been talking about online in the past week. A 1997 US law mandated the registry’s creation, requiring researchers from 2000 to record their trial methods and outcome measures before collecting data. The study found that in a sample of 55 large trials testing heart-disease treatments, 57% of those published before 2000 reported positive effects from the treatments. But that figure plunged to just 8% in studies that were conducted after 2000. Study author Veronica Irvin, a health scientist at Oregon State University in Corvallis, says this suggests that registering clinical studies is leading to more rigorous research. Writing on his NeuroLogica Blog, neurologist 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. Irvin and her co-author Robert Kaplan, chief science officer at the Agency for Healthcare Research and Quality in Rockville, Maryland, focused on human randomized controlled trials that were funded by the US National Heart, Lung, and Blood Institute (NHLBI). The authors conclude that registration of trials seemed to be the dominant driver of the drastic change in study results. They found no evidence that the trend could be explained by shifting levels of industry sponsorship or by changes in trial methodologies.  Irvin says that by having to state their methods and measurements before starting their trial, researchers cannot then cherry-pick data to find an effect once the study is over ..."