TUESDAY, March 4, 2014 (HealthDay News) -- Up to 16 percent of current clinical trials in the United States do not fall under federal regulations that protect the rights and safety of study participants, new government research finds.

Investigators found that of nearly 24,000 active clinical trials, an estimated 5 percent to 16 percent fell into the category of "gap trial." That meant they were not subject to the two federal programs that oversee "human subjects protections" -- such as requirements to ensure patients' informed consent.

Experts said it's not clear what to make of the findings, reported as a research letter in the March 5 issue of the Journal of the American Medical Association.

Trials that are not subject to the federal programs may still have patient-safety monitoring in place, said Karen Maschke of the Hastings Center, a research institute that focuses on bioethics.

"It's hard to know what the data mean. We definitely can't say these trials had no oversight," said Maschke, who was not involved in the study but does research on clinical trial ethics.

She said that even when a particular trial does not technically come under the federal programs' oversight, it may be following those rules anyway.

For example, if a university medical center runs multiple trials, it may extend federal ethics oversight to all of those studies -- even when an individual trial would technically be exempt.

The current study could not account for that scenario, and it's "likely" the results overestimate the true number of gap trials out there, said lead researcher Dr. Deborah Zarin, of the U.S. National Institutes of Health (NIH).

Still, Zarin said, many people may think that all human research trials fall under the same regulations. "I think the fact that it's more of a patchwork system may be news to people," she noted.

There are two broad federal policies on protecting clinical trial participants: The U.S. Food and Drug Administration's human subjects protections, which cover clinical trials testing an unapproved drug or device; and regulations known as the Common Rule, which apply to any clinical trial funded or conducted by the federal government.

Zarin said it has long been known that many trials end up being subject to both sets of federal regulations, while some others fall into the gap. A trial would technically fall beyond the regulations if it had no federal funding and was testing a treatment other than a drug or medical device -- such as a surgical procedure or a behavioral therapy.

Until fairly recently, though, there had been no good way to know how many trials fall into the gap, Zarin explained.

For the current study, her team used data from the NIH's ClinicalTrials.gov -- a registry of clinical trials taking place around the world. The site has been around since 2000, but initially included mostly NIH-funded trials. Since then, it has expanded, and now allows some estimate of the number of gap and non-gap trials.

Zarin's team found that of 23,936 trials active in the United States as of September 2013, 55 percent to 65 percent were covered by the FDA rules only, while 6 percent to 10 percent were covered by the Common Rule alone. Another 19 percent to 24 percent were subject to both sets of rules.

That left between 5 percent and 16 percent that were covered by neither federal regulation. The estimates ranged depending on the definition the researchers used for an FDA-"covered" trial.

Zarin agreed that the numbers leave a lot of questions unanswered. Trials that fell into the gap in this study could be subject to state regulations, or oversight from the institutions running the study or the trial sponsors.

"This is a first view from 20,000 feet," Zarin said. "We can't see perfectly what's going on, but this gives us a first glimpse."

She and Maschke both said that further research is needed to see what is happening with those gap trials -- including where they're being done, and who is overseeing the ethical standards.

"The good news," Maschke said, "is that most of the trials we would be recruited for -- the studies of new drugs and devices -- do come under these (federal) regulations."

More information

The U.S. National Institutes of Health has more on clinical trial participation.