Home tests could help in the fight against the coronavirus. So where are they?

Although no single test will end the pandemic in the United States, experts say the ability for people to take a test at home and know within minutes whether they’re infected could be an important component in stanching the spread of the virus.

Such a test could be taken several days ahead of a visit with grandparents, for example. Or before heading into work. And if a local outbreak occurs, officials could hand out hundreds of at-home rapid tests to find and stop viral transmission.

“At a time when so many people feel like they’ve lost control of so much of their lives, it would put power back in their hands,” said Mara G. Aspinall, a biomedical diagnostics professor at Arizona State University “That’s no small thing.”

Some retailers, including Costco, have begun selling home tests to consumers, but they are costly — about $130 — and require people to mail their sample to a lab and wait 24 to 48 hours for results. The rapid tests now being developed could cost as little as $5 and take 15 minutes for results.

At least two dozen companies are trying to develop home tests, most of them antigen tests that detect proteins on the surface of the virus. Some companies are tantalizingly close to clearing final barriers.

In July, the Food and Drug Administration issued guidelines making clear that any home test needs to be accurate and easy enough for untrained people to use without confusion.

Since then, the agency has not received any applications from companies for home tests, the agency said.

“It is hard to do. There’s a reason no one has gotten FDA approval yet,” said James Li, founder and chief executive of Cellex, a biotechnology company that has been working for months on an at-home test. The FDA is requiring that antigen tests sold directly to consumers be more accurate than most antigen tests to date, because consumers at home will be left to interpret the results on their own.

Li said the challenges to developing home tests are significant but not insurmountable. He would not say how close his company is to meeting those requirements but said his firm and others recognize that with cases rising, such a test could prove useful this winter.

“You don’t want people who are possibly infected going into clinics and hospitals to get tested,” Li said. “A home test addresses that problem.”

Fearing their stringent guidelines may seem onerous to companies, FDA officials wrote an op-ed last month clarifying their expectations.

The officials said that if some home tests fall short on accuracy, one option might be to sell them but require a doctor’s prescription or consultation. Or they could be sold in packs of two or three, using multiple tests to compensate for loss of accuracy.

“Our recommendations are just that — recommendations,” the officials wrote. “We welcome developers with alternative proposals to come talk with us.”

Experts, however, have expressed skepticism and concern about widespread use of such tests. More evidence is needed, they say, pointing to the false results that rapid antigen tests sometimes generate and the logistical problems associated with collecting data on their results — data that are invaluable to public-health officials responsible for tracking the pandemic and attempting to slow it.

Because antigen tests are less sensitive, they can produce false negatives — causing people to think they’re fine when they are in fact infectious. In recent weeks, there also have been increasing incidences of false positives — when people are identified as being infected but aren’t.

Health officials in Nevada ordered nursing homes to stop using antigen tests but reversed course when Trump administration officials threatened to take action against them. Officials in Maine and Vermont and National Football League teams also have encountered recent instances of false positives.

“We don’t want to overpromise. Home tests are not going to solve all the problems. They are just one piece of the puzzle,” Li said.

People screening positive on the home antigen tests could have their status confirmed with polymerase chain reaction (PCR) tests — a molecular process that is more precise but more expensive and takes longer.

Experts said home tests could make an outsize difference in areas at high risk for outbreaks and in rural areas.

“Imagine at the very beginning of an outbreak if you could arm contact tracers with these rapid antigen tests,” said Yuka Manabe, an expert in infectious-disease diagnostics at the Johns Hopkins Bloomberg School of Public Health.

One of the newest antigen tests, the Abbott BinaxNOW, uses a small paper card, costs $5 and can yield results in 15 minutes. Using a shallow nasal swab, the test yields results that can be read from the card like a pregnancy test — a color-coded line indicates testing positive. The test has been deployed mainly in nursing homes and schools, and administered by health professionals.

Some experts argue that the less sensitive nature of antigen tests could actually be an advantage, because they could be effective at catching those with the most viral load when they are most contagious.

The main advantage, however, is their speed and low cost, making them easier to scale up to meet the demand for more testing. The molecular PCR tests that are most commonly used can cost upward of $100 each. It remains unclear whether home tests would be covered by private health insurance plans and the nation’s major government health plans, Medicare and Medicaid, because they would often be used to test people who do not have symptoms.

About 30 million coronavirus tests a month are being conducted in the United States, according to the Covid Tracking Project, a volunteer initiative chronicling the pandemic. But the country needs about 193 million tests a month just to address outbreaks in nursing homes and to reopen schools, according to a recent Rockefeller Foundation report. Other experts have argued that even larger-scale testing is needed.

One reason antigen tests are a powerful tool for screening large numbers of people is they don’t require a large lab to produce results. They can be performed wherever needed at points of care, including nursing homes, schools and clinics.

By January, U.S. companies may be able to produce almost 200 million such point-of-care tests a month, said Aspinall, who researched industry production capacity for the recent Rockefeller Foundation report. By April, they may be able produce almost 230 million a month.

Increasing U.S. testing on such a scale could bring a sea change to the country’s pandemic response. “But it all depends how we use them,” Manabe said.

One significant problem looms with home tests: collecting the results.

Because labs are not involved in such tests, there is no way to report the results. Without that data, the country would be flying blind as it navigates later stages of the pandemic, experts fear.

“It’s not an insurmountable problem, but we need to think big to tackle it,” said Michael Mina, an infectious-disease expert at the Harvard School of Public Health. “The federal government should be working with companies like AT&T, Apple and Verizon to tackle it. Why not make it reportable via a text message? ‘Did you take a rapid test? If positive, press 1.’ ”

Another fear is that rapid home tests could give people a false sense of security.

“There’s a misperception that one negative test means you’re not at risk,” said Mark McClellan, FDA commissioner during the George W. Bush administration and now director of the Duke-Margolis Center for Health Policy.

Although many have compared the design and ease of future home tests to pregnancy tests, he said, “the difference is you can test negative in the morning and be positive by night. It’s likely to work best when done on a repeated, ongoing basis. We don’t have the capacity quite yet to do that.”

It also remains unclear how willing people will be to adopt frequent, widespread home testing.

“It can’t be the only thing we’re doing,” said Gigi Kwik Gronvall, a testing expert at the Johns Hopkins Center for Health Security. “Because it depends on collective planning and action. We can’t even get our act together on masks. It’s unclear whether we would be able to do so on home testing.”