Biotech and pharmaceutical companies have a mixed record when it comes to publishing the results of clinical trials. A peer-reviewed publication that suggests a drug is effective provides a scientific stamp of approval. Studies revealing that drugs are little better than placebos, however, do a company few favors, and companies make little effort to publish them. This can result in a significant publication bias that produces unrealistic expectations regarding the effectiveness of drugs, as we have recently seen with antidepressants.

Last week's edition of Science includes a Policy Forum that discusses the changing state of public access to clinical trial data, which includes many other examples of significant information that never got published. These include recent news, such as negative outcomes in people using Avandia, as well as older problems, such as the well-documented issues with the use of Paxil by teens and Vioxx by nearly everyone.

In many of these cases, the public only learned of the existence of this clinical trial data during legal action. These cases may not be exceptional, either; the authors cite data showing "that over 30 percent of trials of 12 antidepressants submitted to the Food and Drug Administration (FDA) for review, primarily those with negative results, have not been published."

The authors, both based at the US National Library of Medicine, are decisively in favor of greater public disclosure. "Although advances in all areas of science depend upon free exchange of data," they write, "clinical trials warrant particular scrutiny due to their use of human volunteers and our dependence upon their results to inform medical decisions."

The Science article describes the changes that are resulting from the passage of a 2007 law (PDF) that ordered the FDA to create an expanded registry that tracks the results of clinical trials. Thanks to the changes, any trials of drugs or devices regulated by the FDA (other than Phase I safety tests) performed in the US need to be registered. That data is going into a preexisting online database, and the editors of medical journals have made registering there a mandatory precursor of publication in the peer-reviewed literature.

The authors consider the law a major step forward that will increase the access of researchers to relevant clinical data, which will in turn enhance the public's knowledge of critical medical information. Still, there are a number of limitations that will leave holes in the knowledge base. Perhaps the largest black box will be the large and growing set of pseudomedical interventions out there. Ads for diet pills regularly claim clinical validation of their efficacy but, given that they're unregulated, their makers won't be required to post the ostensible clinical data to back that up. Even real medical interventions, such as surgeries and behavioral therapies, don't fall under the FDA's umbrella.

Potential problems don't end there. The authors also recognize that the clinical trial registry will be no panacea for intentional fraud or poorly-designed trial protocols. Much of what we know about drug safety, they also note, has not come from clinical trials but instead is provided by observational studies that describe what happens when drugs enter the market and are used by far larger populations; these studies won't show up in the data registry.

Despite these limits, the existence of the registry will greatly expand the research community's access to trial data. Having the data there, however, won't necessarily provide a direct benefit to the public. People will have to know what to search the database for and qualified individual will still need to analyze the contents in order to extract useful knowledge. Even once the knowledge is out there, action by the FDA is likely to be as politicized and controversial as it is in the absence of such data.

Congress' effort to enforce full disclosure appears to have created a useful resource for the research community and, ultimately, the public. It's not comprehensive, and it won't help us decide how to act on that knowledge, but it's clearly a step that should prevent publication bias—both intentional and incidental—that keeps the public from having a better picture of major health issues.

Science, 2008. DOI: 10.1126/science.1119685