Companies formulating such tests say they won’t seek emergency authorization from the Food and Drug Administration until later this year or early next — in part because the agency wants them to prove that adults of different ages, education levels and English proficiency can successfully use their products.

Public health experts say FDA’s caution is warranted, because a test that’s unreliable or hard to use could help the virus spread. There is also a risk that many people will interpret a negative result as an all-clear; in reality, even the best test will produce some false negatives. And even a true negative does not guarantee that a person is not in the early stages of infection.

“If this was a disease that only impacted the individual, then it wouldn’t be such a problem,” said Georges Benjamin, executive director of the American Public Health Association. “The problem is that there will be a cohort of people who will take the test, find out that they are presumably negative, but they really weren’t, and go out and infect other people.”

A false negative result could be especially dangerous if “people use it to decide whether to go to parties,” said Heather Pierce, senior director for science policy at the Association of American Medical Colleges. “You’ve got infected people feeling like they have a passport to not engage in the other public health measures that we need to suppress the virus.”

False positive results are also a concern, because some people could isolate for up to two weeks, missing work or school for no reason. But that risk could be lowered with follow-up lab-based testing, and pales in comparison to at-home tests’ potential to prevent Covid-19 spread, said HHS testing czar Brett Giroir.

There is little precedent for at-home infectious disease testing. The FDA has only approved one such test — for HIV, made by OraSure Technologies — that does not require oversight by a health care provider. But that green light in 2012 came after a quarter century of debate over the risks posed by false negatives from at-home HIV tests and whether users would get adequate counseling about their results.

Still, FDA officials are eager for companies to bring home Covid-19 tests to market, because they could help expand access to testing and shut down chains of transmission.

“We haven’t received a submission for an at-home test — whether it be molecular or antigen — that we can even review,” FDA diagnostics director Tim Stenzel said last Wednesday. “I’ve let our staff know that I would be very interested in them authorizing a good home test as soon as possible.”

The agency said in July that any at-home test should be able to diagnose at least 90 percent of infections in people with and without symptoms, and should have a false positive rate of 1 percent or less. Companies must also prove to regulators that people will be able to perform the test on their own, without help from a health professional, and provide consumers clear information about when to use the tests and how to interpret the results.

Mark McClellan, a former FDA commissioner under George W. Bush, said the agency’s standards would be “really challenging” for manufacturers to meet for a single-use test.

But the agency has told companies that its accuracy standards are a starting point. FDA officials have said they are open to authorizing tests that don’t meet the 90-percent detection threshold if test makers devise strategies, such as repeated screening over a period of time, that mitigate the lower accuracy.

FDA’s willingness to be flexible is welcome, but not enough, says Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health and a leading advocate for frequent, rapid testing. Mina says that at-home coronavirus testing should be used for surveillance — to detect new clusters of infection — but people should not rely solely on these tests to make medical decisions.

“We really need to have the FDA start to have a little bit of imagination with regard to how these tests are being evaluated,” Mina said. “We continue to see the FDA only approve tests through a clinical diagnostic lens.”

He said that positive results from at-home tests should be confirmed with a second test that uses a different approach to detect the virus — reducing the risk of false positives that could erode public confidence in at-home testing.

Another challenge for test developers is how to ensure results from at-home screening reach state and local health departments.

Automatic electronic reporting of results to public health authorities when an at-home test is run would be ideal, according to Mara Aspinall, a professor of biomedical diagnostics at Arizona State University. “We need to focus on as quickly as possible having that interconnectivity so that we can get an accurate count of both positives and negatives from these tests,” she said.

But although the FDA wants results from at-home tests to be easily reportable, it is not requiring companies developing such tests to build automated systems for doing so. “We know there are developers for at-home and point-of-care [tests] that are trying to build in those reporting capabilities, and that is certainly their choice,” an agency official told POLITICO.

If at-home testing becomes widespread and the results are not tracked, it could hamper the nation’s fight against the coronavirus, said Peter Lurie, president of the Center for Science in the Public Interest and a former FDA associate commissioner.

“If it becomes a significant player in the market and we have no idea what the results are, I think that could be a problem,” Lurie said.

If the FDA gives emergency authorization to an at-home test that doesn’t have an automated system in place to report results, the federal government should consider launching a public information campaign to encourage voluntary reporting to public health authorities, said Marcus Plescia, the chief medical officer of the Association of State and Territorial Health Officials.

“We have to go beyond the responsibility of the FDA to come out with regulations and the responsibility of the manufacturer to have written instructions and warnings for the customer,” he said. “It has to be more proactive and engaging with the public.”

Reeve Benaron, CEO of Intrivo Diagnostics — which is distributing a rapid Covid-19 test that requires a prescription — said that FDA is facing a tough balancing act when establishing its regulatory threshold. But he believes diagnostic companies will be able to meet the bar the agency has set.

“I think you’re going to start to see [at-home tests authorized] next year,” Benaron said. “This calendar year is going to be tough. We need to see really high quality testing. There needs to be quality control because when you’re dealing with diagnosis it is life and death.”

But even if at-home tests become widely available, they will not be a panacea, warned Benjamin from the APHA.

“We have to start messaging now that wearing a mask, washing our hands and social distancing is the process we’re going to be living through for the next several years,” he said. “Our lives are not going to be back to the way they were.”

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