Research without results: inadequate public reporting of clinical trial results

In order to increase transparency in the medical literature, the Food and Drug Administration (FDA) Modernization Act of 1997 and the FDA Amendment Act of 2007 required registration of all "applicable trials" with required "basic results" reporting. We evaluated the rate of compliance with the FDA mandatory results reporting in www.clinicaltrials.gov.

All completed registered interventional studies that may be subject to FDA regulation, one year prior to required results reporting (October 2006 to September 2007, n = 1097) and during the two years after required reporting (October 2007 to September 2008 (07-08), n = 2231 and October 2008 to September 2009 (08-09), n = 2923).

Downloading all 99,315 records from clinicaltrials.gov, we excluded all non-applicable studies. Results reporting increased from 6.8% (n = 75) prior to mandatory reporting to 19.1% (n = 427, p<.01) in 07-08 and 10.8% (n = 316, p<.01) in 08-09. The odds ratio for results reporting using the 06-07 time period as the reference was 3.31 (95% CI 2.54-4.32) for 07-08 and 1.74 (1.33-2.28) for 08-09. Of the 818 trials with results in clinicaltrials.gov, the rate of published articles found decreased from 60% (n = 45) in the year prior to required reporting to 33% (n = 140, p<.001) for 07-08 and 20% (n = 63, p<.001) for 08-09 time period.

The majority of studies registered in clinicaltrials.gov are not required to report data. Of studies that may be required to report data, compliance with data reporting has improved. The clinicaltrials.gov website is not yet a comprehensive resource for study results.