Tests and reviews of drugs that are supported by the pharmaceutical industry should perhaps be read with more than a hint of skepticism. So advises a new study in the British Medical Journal, which finds these industry supported reviews are more likely to reach favorable conclusion on drugs, than independent reviews.

According to the authors, bias in drug trials is common and often favors the trial sponsor's product. To balance this effect, independent reviews -- which can have a more critical and systematic approach -- are essential to ensure doctors and other health professionals have the information they need.

The authors, based in Denmark, compared the results of 24 pairs of reviews conducted by different people on the same drugs.

Compared to reviews supported by the pharmaceutical industry, reviews undertaken by the Cochrane Collaboration -- an independent body -- were of a higher quality and were more likely to address the potential for bias in the review.

Of seven industry-supported reviews, all recommended the experimental drug without reservation, while none of the corresponding Cochrane reviews reached the same conclusion.

Six of the eight Cochrane reviews analyzed had reservations about the quality or relevance of the trials or their findings and two of them noted that the effect decreased with increasing number of patients in the trial. Seven mentioned higher cost of the experimental drug as a problem.

In contrast, none of the industry-supported reviews mentioned higher cost as a problem, and two claimed that the experimental drug was cost-effective.

The researchers also found that the reviews with not-for-profit support or no support had cautious conclusions similar to the Cochrane reviews.

The authors conclude that industry-supported reviews should be read with caution. They also want greater transparency, including the inclusion of more information on methodology and the estimated effects of the drugs, in order to allow readers to judge the reliability of drug reviews.