Conflicts of interest significantly underreported in systematic reviews of drug efficacy, safety

Systematic reviews seek to answer key questions about the relative effectiveness and safety of medical interventions by selecting, combining, and critically evaluating the research in published medical literature.

But more than two-thirds of the systematic reviews of drug therapies written to the leading international standard fail to include any information on the funding sources of the included studies or the financial conflicts of interest of the authors of the aggregated studies.

The finding is the result of an analysis of such reviews of drug treatments added in 2010 to the database of the international Cochrane Collaboration, which was published last week in the BMJ. The study was co-authored by Lisa Bero, PhD, faculty member and vice chair for research of the UCSF School of Pharmacy’s Department of Clinical Pharmacy. She is also co-director of the San Francisco Branch of the U.S. Cochrane Center.

Published in the peer-reviewed journal The Cochrane Library, Cochrane reviews are “widely recognized as setting the standard for the evaluation of healthcare interventions,” write Bero and her co-authors from the United States, Canada, and the Netherlands.

How international standard falls short

But they found that only 46 out of 151 Cochrane reviews of drug treatments analyzed reported information on the funding sources of their included studies, and just one-fifth of the reviews provided the funding sources for all their studies. Further, only about 1 in 10 reviews provided information on whether study authors had financial ties to or were employed by the pharmaceutical industry.

Such disclosure is significant, Bero and her co-authors write, because of “the well-documented influence of industry funding of drug trials on their conduct, interpretation, and reporting.”

“A key part of the systematic review is to assess bias in the included studies,” says Bero. “Funding sources and financial conflicts of authors can influence the outcomes of drug studies because industry-funded studies are more likely to have results that favor the sponsor’s product, even when controlling for other methodological biases.”

Thus “guidelines now routinely recommend that study funding and author-industry financial ties be disclosed in published research reports,” write Bero et al. The same is true for the authors of systematic reviews, as well as meta-analyses, which integrate statistical findings from multiple studies.

A gap in reporting funding, ties

But there’s clearly a gap when it comes to reporting the information about conflicts of interest for the authors of studies aggregated in Cochrane reviews.

That gap is even wider for other meta-analyses of randomized control trials of drug treatments published in “high-impact biomedical journals,” according to another Bero-co-authored study in the March 2011 Journal of the American Medical Association. Only 7% (or two out of 29) of such meta-analyses published in the first 10 months of 2009 reported the drug trial funding sources and none reported author financial ties to or employment by the pharmaceutical industry.

According to both the current and prior versions of the Cochrane handbook that guides review conduct and reporting, “review authors should extract data on the funding sources of included trials and may consider extracting data on trial author-industry financial ties,” the new analysis notes. But such conflict-of-interest reporting in reviews is optional.

The co-authors of the new BMJ analysis call for a new Cochrane policy “to require authors of systematic reviews and meta-analyses to report the funding sources of all included trials or to report that trial funding sources were not disclosed.”


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