Half of all drug studies that are recorded in a large Web-based, federal registry, ClinicalTrials.gov, haven’t been published in a journal, a study finds. The selective publication of health studies could restrict doctors from carrying out optimal evidence-based medicine, which relies on reviewing and evaluating clinical outcomes that are communicated in peer-reviewed journals.

Carolina Riveros, of the French Institute of Health and Medical Research, and colleagues analyzed the proportion of 594 randomized controlled drug trials carried out in 2009 that made it into a publication. They found that 297 (50%) of these drug studies posted in ClinicalTrials.gov lacked a corresponding article in any medically recognized journal, despite being completed an average of three years before Riveros and her colleagues' assessment.

"Our results have important implications for several stakeholders: patients and clinicians, authors, researchers performing systematic reviews and meta-analyses, methodologists, peer reviewers, developers of reporting guidelines and journal editors,” the authors commented in their PLOS Medicine study. “[O]ur results outline the importance of registries to improve transparency in clinical research by making information about clinical trials including results publicly available, which is the basis for well-informed decision making about patients' health."

The authors also found that many of the studies that actually did make it into a journal were not as comprehensive as their ClinicalTrials.gov supplement. Furthermore, certain types of outcomes were less likely to be published in journals than posted on the federal website — the most notable being “adverse events” and “serious adverse events” as well as flow of participants, which details the recruitment, treatment, follow-up and analysis of participants.

Although many unpublished trial outcomes are eventually published years later, the authors concluded that their study “highlight[s] the importance of extracting efficacy and safety data posted at ClinicalTrials.gov for trials whose results are not yet published but also for those with published results because … reporting was more complete at ClinicalTrials.gov.” They suggested implementing templates that allow for standardized reporting of trial results in journals “or broader mandatory registration of results for all trials may help further improve transparency."

The results of the Riveros study agrees with a 2009 study in PLOS Medicine, which also found varied reporting of completed trials and certain kinds of data. The authors of that study emphasized the importance of evidence-based medicine, which “can only be effective if all the results from clinical trials are published promptly in medical journals,” they wrote. “Unfortunately, the results of trials in which a new drug did not perform better than existing drugs or in which it had unwanted side effects often remain unpublished or only appear in the public domain many years after the drug has been approved for clinical use by the US Food and Drug Administration and other governmental bodies.”

Source: Riveros et al. Timing and Completeness of Trial Results Posted at ClinicalTrials.gov and Published in Journals. PLOS Medicine, Dec 03, 2013 DOI: 10.1371/journal.pmed.1001566