The Food and Drug Administration on Saturday took new steps to sharply expand testing for the novel coronavirus by allowing certain hospital laboratories to use their own tests before they are cleared by the agency.

The action, which also covers commercial labs, followed complaints from academic medical centers that the previous policy — which required prior approval of the lab tests — was too burdensome and slow and was impeding efforts to diagnose cases of the coronavirus.

Experts have warned that the small number of U.S. cases so far may be a reflection of limited testing, not of the virus’s spread. Testing has been hobbled because of problems, now being corrected, involving the only test that had been cleared by the FDA, one created by the Centers for Disease Control and Prevention.

Certified hospital labs typically can develop their own tests for in-house use, but the rules of a public health emergency — which are now governing the coronavirus outbreak — mean those tests need “emergency use authorization” from the FDA. Under the policy announced Saturday, the labs can begin using their own tests after validating them and before the FDA has finished the reviews. As a result, scores of labs could soon begin testing thousands of patients.

“We believe this policy strikes the right balance during this public health emergency,” FDA Commissioner Stephen Hahn said in a statement. “We will continue to help to ensure sound science prior to clinical testing and follow-up with the critical independent review from the FDA, while quickly expanding testing capabilities in the U.S.”

He said the agency wasn’t changing its standards for issuing emergency use authorizations but was responding to a “dynamic and evolving situation.”

Michael Mina, the associate medical director of clinical microbiology at Brigham and Women’s Hospital in Boston and a critic of the previous policy because of the delays it caused, called the change “a big win” for public health. “It’s essentially giving a very clear avenue forward to start testing almost as soon as any laboratory can get their test actually running. There’s essentially an avenue to really start testing patients.” He said hospital labs probably could get tests set up and begin validating that they are working within a week under the new policy.

The policy is “significantly improved,” said Alex Greninger, assistant director of the virology division at the University of Washington Medical Center in Seattle.

But Melissa Miller, director of the clinical microbiology laboratory at the University of North Carolina School of Medicine, said the change fell short. “To still have to file the [request for emergency use authorization] is disappointing,” she said. She called the requirement “burdensome and unnecessary,” given that the labs in question already are certified to do high-complexity testing.

The FDA policy goes into effect immediately. The agency said that after completing their test validations, labs should notify the FDA that the tests have been verified. Labs should then submit completed emergency use authorization requests within 15 business days.

“We believe this action will support laboratories across the country working on this urgent public health situation,” said Jeff Shuren, director of the FDA’s Center for Devices and Radiological Health.

Separately, the testing capacity of public health labs, which was low because of a problem with the CDC test, is starting to rise sharply. Scott Becker of the Association of Public Health Laboratories said 41 labs will be able to use the CDC test by Monday. And more labs will come online in the following days, boosting the daily testing capacity to 10,000 patients by the end of the week, said Becker, executive director of the lab association.

In a letter to congressional health leaders on Friday, dozens of big hospital labs complained that they were not able to move forward with their own coronavirus tests until they were reviewed by the FDA. “This regulatory process is significantly more stringent than that required for every other virus” the clinical laboratories test for, the letter said. It noted that no test manufacturer or clinical laboratory had successfully navigated the FDA process for coronavirus yet; only the CDC test had been cleared.

“This creates undue pressure on CDC and state public health labs to rapidly scale manufacturing and clinical testing,” and as a result, the turnaround may be slow, the letter said. It added that many clinical laboratories across the United States already have validated tests for the virus and “could begin testing tomorrow.”

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