Researchers at Children's Hospital Boston have released a report that says that when published results are systematically tracked for drug trials registered with ClinicalTrials.gov, those from industry-funded trials are the likeliest to be favourable to the drug in question. In the August 3 issue of the Annals of Internal Medicine, the researchers call for more public disclosure about clinical drug trials at their outset to reduce the possibility of bias in findings.
The research team, led by Dr. Florence Bourgeois of Children's Division of Emergency Medicine, and Dr. Kenneth Mandl, Laboratory Director in the Children's Hospital Informatics Program, reviewed 546 drug trials conducted between 2000 and 2006 and listed with ClinicalTrials.gov, a web-based federal registry of clinical trials. The researchers scanned the medical literature for publications associated with each trial, checking four separate databases and contacting trial investigators directly if necessary.
Overall, allowing for a three-year lag time from the completion of the trial, two-thirds of the trials had published results. The industry-funded trials reported positive outcomes 85 percent of the time, as compared with 50 percent for government-funded trials and 72 percent for trials funded by nonprofits or non-federal organisations. In addition, among the nonprofit/nonfederal trials, those that had industry contributions (nearly half) were more likely than those without to report positive outcomes (85 vs. 61 percent). These differences were all statistically significant. The researchers acknowledge that the pharmaceutical industry was probably more selective in which trials it funded, helping to account for their greater proportion of favourable outcomes.
The industry-funded trials were in more advanced phases of study - 89 percent were Phase 3 or Phase 4, versus just 51 percent of government-funded trials and 65 percent of nonprofit/nonfederally-funded trials. However, even Phase 1 and 2 trials funded by industry reported the highest percentage of favourable outcomes.
In addition, industry-funded trials were the least likely to have published results within two years of study completion (32 percent) as compared with trials with no industry contributions (54 percent for government trials, and 56 percent for purely nonprofit/nonfederal trials). As the researchers discuss in the paper, clinical trials can be manipulated in various ways to make the results appear more favourable. Publication bias - a tendency to selectively publish only positive results of a trial, or delay publication of negative results - is one factor that has received much attention, as in a 2008 study of antidepressants in The New England Journal of Medicine.
The use of registries like ClinicalTrials.gov, launched in 1999, was hoped to reduce publication bias by creating a record for all clinical trials. In addition, in 2005, the International Committee of Medical Journal Editors began requiring that a trial be registered before enrolling patients in order to be considered for publication, thus creating a record of the planned study outcomes before the study's initiation. In 2007, the FDA expanded the scope of Clinical Trials.gov, requiring the sponsors of all drug, biologic and device trials to register their studies upon launch (phase I trials excepted).
The study was funded by the National Library of Medicine and the National Institute of Child Health and Human Development.
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