More and more, policy decisions and what medications doctors prescribe for their patients are being driven by large 'studies of studies' called meta-analyses, which statistically combine results from many individual drug trials.

There's a problem, though.   A group analyzing meta-analyses writes in the Journal of the American Medical Association (JAMA) that important declarations of financial conflicts-of-interest in individual drug trials disappeared when those studies were combined in meta-analyses.

In other words, the information was right there, it wasn't hidden in the studies themselves.

They reviewed 29 recent meta-analyses on a range of drug treatments published in high-impact medical journals. Those 29 meta-analyses included results from 509 drug trials. The team documented the funding sources and author-industry financial ties of all 509 trials and whether or not the meta-analyses noted who had funded the trials.

"Only 2 of the 29 meta-analyses even mentioned the issue of who funded the original drug trials, and even those 2 did it in very obscure places in the published articles," said Dr. Brett Thombs, a psychologist and assistant professor in the Department of Psychiatry at McGill University. "Not one of the meta-analyses mentioned whether researchers who conducted the trials were employed by industry or personally received money from industry."

"Most people want their physicians to make treatment decisions based on high-quality, unbiased evidence," said McGill graduate student Michelle Roseman, first author of the paper. "Researchers who conduct meta-analyses should be aware of who funds the trials they review and they should assess the risk that findings might be biased due to drug company sponsorship."

The team identified 7 meta-analyses where every single drug trial included was paid for, at least in part, by the maker of the drug or had investigators linked financially to drug makers. In 6 of the 7 meta-analyses, however, there was no mention of who funded the drug trials.

"Consumers can be more confident that drugs actually work if there is at least 1 independent evaluation that confirms this," said Thombs. "When all existing studies are financially linked to drug makers, there is a risk that patients and their physicians may be misled."

"What is surprising is that many researchers who do meta-analyses don't seem to be aware of these important issues," added Roseman. "We surveyed the authors of the 29 meta-analyses. Only 7 said that they even recorded who funded the drug trials they evaluated, and only 2 published this information. Furthermore, only 2 recorded author-industry financial ties, and none published this."

They have called for changes in policy on how evidence on drug treatments is reported in meta-analyses. "Unless we require authors of meta-analyses to provide this information for consumers, it will be lost," emphasized Thombs. "Patients and doctors want to have this information, and we believe it is in the best interest of all of us to make sure it is available."

"Few people would buy a car whose performance and safety had only been tested by the manufacturer or a house based only on the word of the seller without an independent inspection," added Thombs. "Yet most drugs that people take have been evaluated, for the most part, by the companies that produce them and profit from their sales. At the very least, doctors and their patients need to know who is evaluating the effectiveness and safety of drugs that are being prescribed."