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Publication bias in drug trials

PLoS Medicine has published a research article that has assessed the publication rate of efficacy trials submitted to the Food and Drug Administration (FDA) in approved New Drug Applications (NDAs).

The research examined efficacy trial data contained in NDAs submitted in 2001 and 2002 and tried to identify corresponding published clinical trials. 164 efficacy trials were identified with subsequent publication identified for 78% (n = 124). Statistical analysis found that trials with favourable primary outcomes or active comparators were more likely to be published.

The study also found that the statistical significance of the study changed between submission to the FDA and final publication with four of these changes being in favour of the study drug (p=0.38). Nine conclusions changed between the FDA submission and final publication with all the changes favouring the study drug (p=0.0039).

It is also interesting to note that more than 20% of efficacy trials submitted to the FDA remain unpublished 5 years after approval. The authors conclude that, "the information that is readily available in the scientific literature to health care professionals is incomplete and potentially biased".

Action: Clinicians should be aware of the potential for publication bias. Cautious use of drugs with limited data would seem prudent until more data are available to support efficacy claims.