The team, led by Erick Turner from Oregon Health & Science University in Portland, USA, explain:
"Selective reporting of research results undermines the integrity of the evidence base, which ultimately deprives clinicians of accurate data for prescribing decisions."
The researchers examined 24 FDA-registered pre-marketing trials for 8 second-generation anti-psychotics - ziprasidone, aripiprazole, olanzapine, risperidone, iloperidone, risperidone long-acting injection, quetiapine, and paliperidone. The team then compared these trials with the results announced in subsequent reports published in medical journals.
They discovered that 4 pre-marketing trials submitted to the FDA demonstrated negative results and were never published. One trial revealed that the new medication was statistically inferior to a considerably cheaper competing drug, while three trials showed that the new drug had no statistically significant benefit over placebo.
The authors found that in the published trials, some reports embellished on the effectiveness of the new drug. For instance, the FDA review revealed that iloperidone was statistically inferior to 3 different competing medications, although this information was not reported in the corresponding reports published in medical journals.
However, using a meta-analysis to combine trial data and comparing all 8 medications to placebo, the researchers found that publication bias did not greatly affect their overall apparent efficacy. The researchers state that some negative information was not reported and was of more concern as it could potentially mislead clinicians.
The researchers conclude:
"The magnitude of publication bias found for anti-psychotics was less than that found previously for antidepressants, possibly because anti-psychotics demonstrate superiority to placebo more consistently.
With further studies investigating publication bias in other drug classes, a more accurate evidence base can emerge. To that end, increased access to FDA reviews has been advocated. At the present time, the FDA is not as transparent with its clinical trial data as it could be.
It is encouraging that the FDA has convened a Transparency Task Force. If the agency fulfills its mission to increase transparency, the public health will surely benefit."