Participants uninformed in some halted trials.

When Congress passed a bill last month requiring makers of drugs and medical devices to disclose the results of clinical trials for all approved products, advocates of greater study disclosure applauded the move.

But a provision that would have mandated disclosures for another group of products never made it into the final version of the bill. It would have covered products tested on patients, but dropped before marketing, "The New York Times" reported Oct. 30.

"Trial sponsors can still choose to keep information about some trials confidential, creating serious ethical concerns," said Deborah Zarin, M.D., the director of ClinicalTrials.gov, a Web site run by the National Library of Medicine.

Many experts said the recent Congressional debate underscored a troubling fact: some patients in clinical studies never learn about test results. The problem may be particularly relevant to those implanted with medical devices that stay with them long after a trial is over.

For manufacturers and researchers alike, "there is a tremendous incentive to go on, to forget about the old and move on to the new," said Drummond Rennie, a deputy editor at "The Journal of the American Medical Assn.," who has written critically about clinical trials.

There are no data available for the number of patients who participate in studies of drugs and medical devices that never make it to the marketplace, though it is likely that the number runs into the thousands.

Although researchers conducting clinical studies are not required to disclose test results to study participants, they must alert patients taking part in a test to emerging product dangers. Companies also have to keep promises made to regulators at the time a trial began, like agreements to follow the health of study patients. Such promises are often required to get approval to begin trials in the first place.

But researchers and manufacturers do not always fulfill even those minimal requirements, The Times stated. And such failing may be particularly acute in trials of implanted devices, since those products remain inside patients.

In August, for example, FDA sent a warning to Boston Scientific after investigators discovered the company's diligence in following up with patients faltered around the time it dropped a product under development --an experimental stent intended to prevent the rupturing of an aneurysm in the major abdominal artery.

Agency investigators found that Boston Scientific, which halted development of the stent last year after a study showed it frequently fractured, had neglected to tell patients in that trial about the problem's scope. Researchers involved said such a fracture, while not dangerous in itself, could cause a stent device to shift position, thus rendering it useless in treating an aneurysm, a weakening of a blood vessel that can burst with fatal consequences.

Paul Donovan, a spokesman for Boston Scientific, told The Times that the company was moving to address FDA's concerns. While six patients involved in the study have died, Donovan said that the company did not believe that those deaths were related to either the stent or burst aneurysms.

Because of loopholes in the recently passed Congressional bill, device makers like Boston Scientific will still have discretion whether to publicly reveal the results of studies like that of the failed stent.

Under the law, device producers will have to report such pre-marketing studies and their results to FDA, but that data will remain in a confidential "black box" until a product is approved; if a device is rejected or dropped, a company will not have to disclose those results or even publicly acknowledge that the trials occurred.

Device makers lobbied against mandating disclosure for failed products, arguing that releasing such data would be confusing to patients and would give away valuable information to a company's competitors about devices under development that might succeed in subsequent trials.

The new bill does allow for a mechanism under which the Secretary of Health and Human Services could release trial data about unapproved products if a public health issue exists, but such moves would be argued case by case.