Almost a third of large clinical trials in the US still not published five years after being finished, scientists write in BMJ

Drug companies and other organisations that carry out clinical trials are violating their ethical obligation to the people who take part by failing to publish the results, scientists will argue on Wednesday.

Almost one in three (29%) large clinical trials in the United States remain unpublished five years after they are finished, according to scientists writing in the British Medical Journal. Of those, 78% have no results at all in the public domain.

The scientists calculate about 250,000 people took part in the unpublished trials and have therefore been exposed to all the risks involved in research without the benefits to society they were led to believe would ensue. This "violates an ethical obligation that investigators have towards study participants", say Christopher Jones from the Department of Emergency Medicine, Cooper Medical School of Rowan University, New Jersey, and colleagues. They call for additional safeguards "to ensure timely public dissemination of trial data."

The researchers looked at trials registered in the United States, but some of that research will have taken place in Britain and the issue is global.

Drug companies and other organisations with commercial interests have always been reluctant to publish the results of unsuccessful trials and those they think might give useful information to competitors. Academics, too, do not always publish their results.

There has been increasing pressure for all trial results to be made public, especially those funded by the pharmaceutical industry. Concealing a few failures can make a new drug look more effective than it really is or hide side-effects. This led the US to require the registration of all trials and reports of their results on the Clinicaltrials.gov database. But the BMJ paper says the evidence is that the legislation is ignored.

Jones and colleagues looked at 585 trials involving more than 500 volunteers that were completed before January 2009. Five years or more later, 171 were still unpublished and 133 had no results posted on the database at all. Trials funded by industry were more likely not to have been published (32%) than others (18%).

The organisation Sense about Science has been at the forefront of the AllTrials Campaign for full publication. Síle Lane, its director of campaigns, said the US research was very relevant to the UK.

"Clinicaltrials.gov is a global register and the world's largest so it includes trials that were carried out in the UK. Anyway, trials from around the world are used to make UK prescribing decisions. So information from those trials is vital for UK regulators and researchers," she said.

"There's no excuse for not publishing results but a huge public health benefit to having a complete picture of what was found in trials conducted on treatments currently available to patients."

Richard Stephens, a cancer patient and AllTrials campaign supporter, said failing to publish results was a betrayal of people who take part in research. "I have entered five research studies as a participant. I did it for several reasons, but the one motive that runs through every one of them is my belief that by taking part in research I will help other patients in future," he said.

"For that to happen, the results of the research must be made available. Even if the research isn't finished or the results aren't as expected, the data and information are still of value and should be made available.

"I would ask every researcher and every research funder out there to do all they can to make their results available. Patients become participants to add to knowledge and to eliminate uncertainties. Hiding results, no matter what the reason, isn't in that spirit at all. In fact it is a betrayal of our trust."

The House of Commons science and technology committee called for registration and publication of all trials on an accessible database, like that in the USA. Regulation to be debated next week would require all EU clinical trials to be registered and report their summary results within one year of the finish in a publicly accessible EU Clinical Trials Register.