The majority of moderate- to high-risk medical devices approved by the U.S. Food and Drug Administration lack publicly available scientific evidence to verify their safety and effectiveness despite requirements in the law, according to a study released Monday.
Researchers reported in JAMA Internal Medicine that 42 of 50 selected medical devices cleared by the FDA over five years lacked such data, despite a 1990 law calling for sufficient detail to justify their FDA clearance. The law calls for public data about studies, which may include clinical studies, involving human patients.

"If wonderful studies are being done, there is no evidence of this, and there's no way for the public to see it," said Dr. Diana Zuckerman, a study author and president of the National Center for Health Research, a public health think tank in Washington. "It's shocking how little information is available despite an FDA leadership that talks about transparency."
The study's authors, who were from the health-research center, called for better enforcement of that law.
In response to the findings, the FDA said that it "reviews a significant amount of data—far more than what is publicly available." The agency said its approach "has served the American public well by balancing the need for robust evidence to assure safety, while expeditiously bringing new technologies" to the market.
At issue is a type of medical-device approval under which about 400 implanted devices annually—the majority of moderate- to high-risk ones—are cleared by the FDA for marketing.
Under that system, called a 510(K) review, the company doesn't have to conduct studies in human patients, as is generally the case with drug approvals, although it may. Most devices can get FDA clearance simply by showing that they are roughly equivalent to another product, called a predicate device, that is already on the market. The theory is that if the older device has proved safe and effective, the new one should be also.
The 510(K) process has led to cases like metal-on-metal hips, which can leave metal filings in the body.
But the Safe Medical Devices Act of 1990 required companies to make publicly available evidence of why the new product truly is comparable to the old one; the evidence can include studies of patients, known as clinical trials, but it isn't necessary.
The Institute of Medicine, the research branch of the National Academy of Sciences, in 2011 called for an overhaul of this type of FDA clearance, saying in a report that "reliance on substantial equivalence cannot assure that devices reaching the market are safe and effective."
"A lot of these are high-risk devices that get on the market with no studies at all," said Dr. Rita Redberg, medical professor at the University of California, San Francisco, and the chief editor of JAMA Internal Medicine. "When there are studies, they're not available" for the public to see.
She said that she sees no evidence that the leadership of the FDA under the Obama administration has heightened the level of safety assurance required.