LONDON (Reuters) - Unreported data from early trials of experimental medicines in humans can result in harm to future patients and needless costs for health systems, according to scientists writing in the British Medical Journal on Wednesday.

In a series of studies for the BMJ on the extent to which clinical trial data are made public, researchers found a large proportion of evidence was unreported and much of what was reported by pharmaceutical firms was inadequate.

"Missing data is a serious problem in clinical research," the scientists said about their findings. "It distorts the scientific record, so that clinical decisions cannot be based on the best evidence."

New rules set out in 2007 by the U.S. Food and Drug Administration, which regulates the world's largest market for drugs, made publication of a results summary on the website within 12 months mandatory for all eligible trials that were either started or ongoing as of September 2007.

As of 2008, the global drug industry body the International Federation of Pharmaceutical Manufacturers and Associations also required its members -- which include the world's major drugmakers -- to register all trials in patients and publish a summary of the results.

But in the BMJ studies, Richard Lehman from Britain's Oxford University and the BMJ's clinical epidemiology editor Elizabeth Loder described finding a "culture of haphazard publication and incomplete data disclosure."

"The current situation is a disservice to research participants, patients, health systems, and the whole endeavor of clinical medicine," they wrote.

The BMJ has long been campaigning for greater transparency in clinical trials and has attacked the drug industry for being reluctant and slow to publish data from human trials of drugs in the later stages of development, and from trials of medicines already licensed and on the market.

Drug firms, for their part, have been publishing more data from trials they sponsor, but this is sometimes done on obscure websites rather than in high-profile peer-reviewed journals, and critics say the industry is still far from transparent.

In one of the studies, led by Andrew Prayle of Britain's Nottingham University, researchers looked at 2009 and found that only 22 percent of trials registered on and subject to mandatory reporting had results available a year after being completed.

Another study found that fewer than half of all U.S. National Institutes of Health-funded trials are published in a peer-reviewed journal within 30 months of completion.

"Most clinicians assume that the complex regulatory systems that govern human research ensure that this knowledge (from clinical trials) is relevant, reliable, and properly disseminated. It generally comes as a shock to clinicians, and certainly to the public, to learn that this is far from the case," Lehman and Loder wrote in a commentary on the findings.

"When the word 'mandatory' turns out to mandate so little, the need for stronger mechanisms ... becomes very clear."

A third study in the series found that when previously unpublished data are included in meta-analyses of drug trials -- studies which seek to collate all the available evidence to come to a more robust conclusion -- the results are often different.

The researchers said the results showed that "past failures to ensure proper regulation and registration of clinical trials, and a current culture of haphazard publication and incomplete data disclosure, make the proper analysis of the harms and benefits ... almost impossible."

Lehman and Loder warned that patients "will have to live with the consequences of these failures for many years to come" and called for more robust regulation and full access to raw trial data to allow better understanding in future of the benefits and harms of many kinds of medicines.

(Editing by Will Waterman)

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