Even though it's an FDA requirement, most implanted medical devices lack publicly available scientific evidence that shows that they're "substantially equivalent" to devices already on the market, according to a new study published in JAMA.

Researchers at the National Center for Health Research in Washington put together a sample of 50 devices ranging from hip implants to surgical mesh that received FDA approval from 2008 to 2011. They also looked at 1,105 devices that were already on the market.

They found that only eight out of 50 of the devices had publicly available information that showed that they are "substantially equivalent" to devices already on the market. For the devices that were already on the market, only 31 out of 1,105 had sufficient information.
"We repeatedly found that scientific evidence of the substantial equivalence, safety or effectiveness of medical devices was not publicly available in accordance with the legal requirements," the researchers wrote in a statement. "To protect the public health and allow for independent judgment of the quality of the scientific evidence that supports the marketing of medical devices, the FDA should enforce the law."

Another study that was also recently published in JAMA found that the small sample sizes and delays on agreement of protocol might hamper the usefulness of studies that are conducted after the devices get FDA approval.

Researchers at The Pew Charitable Trusts in Washington compiled information from the FDA website on 223 studies that the FDA ordered on 158 medical devices from January 2005 to December 2011. That information included 48 percent of the new high-risk devices that received approval.

They found that if a study protocol was not in place when the device received approval, then an average of 180 days went by before a protocol was agreed upon. During that time, the FDA did not send out a warning letter or penalty for the delays.

They also found that the most common result of the studies was that the FDA asked for a labeling change. Only one out of the 223 studies led to an action other than that.

"We encourage the agency to work together with all stakeholders to evaluate how these studies can more effectively be used to improve the public health," the researchers wrote in a statement.

Dr. Elisabeth M. Dietrich of the University of California, San Francisco and Dr. Joshua M. Sharfstein of the Maryland Department of Health and Mental Hygiene published a commentary in which they discussed the FDA's taking steps to solve those issues.

"At times, the agency has rightfully been criticized for pursuing one goal at the expense of the other," they wrote. "In recent years, the FDA's Center for Devices and Radiological Health has been actively undertaking reforms to advance both goals simultaneously and to improve the scientific rigor of its operations. It is important to recognize and support this progress, even as the FDA's performance continues to be monitored through research and oversight."

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