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Rapid tests for Covid, RSV and flu are available in Europe. What's holding them back in the US?

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Sander Brus didn’t expect a photo of his friend’s grandfather’s flu diagnosis to go viral. But when he shared the image on Twitter in December, he was bombarded with messages, he said.

People in the United States wanted to know how to buy the rapid photo test, which simultaneously screens for three common respiratory viruses: Covid, respiratory syncytial virus (RSV), and two types of influenza, A and B.

The viruses circulated widely this winter and share many of the same symptoms, meaning they are often indistinguishable without a diagnostic test. But unlike Covid tests, which are available over the counter, RSV and flu tests must be performed in a doctor’s office or ordered with a prescription. And the FDA has not authorized a home test that can quickly detect all three viruses at once.

The Brus Photo Rapid Test, however, is available in the European Union, and the manufacturer has certified that it meets EU health and safety standards.

Brus is the founder of Measie, a diagnostics vendor that sells the test online. The test costs 6.5 euros ($6.92), and the company has sold about 10,000 of them so far, Brus said.

The test manufacturer, Shenzhen Microprofit Biotech Co. Ltd., says it catches 100% of negative cases for Covid, flu or RSV – meaning it won’t produce false positives – and detects 90% of influenza B cases, 92% of influenza A cases, 93% of influenza Covid and 95% of RSV cases.

Brus said that performance should be enough to secure authorization in the U.S.

“A test done in Amsterdam, where I’m from, will give exactly the same result as a test done in New York. There shouldn’t be a difference based on geography,” he said. “But still, people in the United States can’t use it and I can.”

Sheng Tang, deputy general manager of Shenzhen Microprofit Biotech, said the company has no plans to apply for emergency authorization for its US trial. Tang said in an email that he doesn’t think the Food and Drug Administration would grant the authorization, given its regulatory restrictions.

Dr. Susan Butler-Wu, an associate professor of clinical pathology at the University of Southern California, said rapid testing for multiple viruses is “the way of the future” and would help more people access appropriate treatments. But the US has historically lagged behind Europe in terms of authorizing new diagnostics, she said.

“It’s not uncommon to see things approved in other countries that are great products and we don’t have them here. That’s just the reality of the situation,” she said. “It takes time to go through the process and get approval.”

The FDA authorized an over-the-counter test that allows people to swab themselves simultaneously for the flu, Covid, and RSV, but the swab must be mailed to Labcorp. The test costs $169 for people without insurance.

The FDA has said it strongly supports home testing for respiratory viruses, including combined testing for flu and Covid. But the agency declined to comment on whether it has received or is considering any requests from manufacturers for such tests.

“When the data is solid, the FDA has not hesitated to act quickly to authorize the trials, with at-home testing of all areas being a high priority for the agency,” an FDA spokesperson said.

The agency pointed to a snag, however: At-home flu tests traditionally required people to swab high up in the nose, which usually means a doctor must administer them.

Unlike Covid tests, Butler-Wu said, there has been less opportunity to study whether rapid flu tests can be administered into the shallowest part of the nose and maintain their accuracy.

“You don’t want people to just touch the outside of their nose and not get the benefit of the test,” said Joshua Sharfstein, a former FDA deputy commissioner, now a professor of health policy and management at Johns Hopkins University.

The Doctor. Michael Mina, chief scientific officer at home-testing company eMed, said the FDA tends to have strict requirements for over-the-counter tests. The agency often asks manufacturers to conduct studies that demonstrate people can properly administer the tests at home — a process that can cost millions of dollars and delay test authorization by months or years, Mina said.

“In the past, it took a long time to authorize new self-tests like HIV tests or even pregnancy tests,” he said. “It took years and years and years and years. We have a very conservative regulatory approach.”

In real life, Mina isn’t concerned about the ease of use of combined tests for respiratory viruses.

“We know Americans can rub their noses because it’s been done millions and millions and millions and millions of times for Covid,” he said.

Even if a doctor administers a rapid test, however, the FDA may still have reservations about its accuracy. Butler-Wu said that rapid flu tests administered by medical professionals typically have around 60% sensitivity, meaning they produce false negatives about 40% of the time. For RSV, that performance is “slightly better” but still unreliable, she said.

“There are longstanding issues with influenza and RSV antigen test performance that have been extremely well documented,” said Butler-Wu. “In 2009, when the new H1N1 appeared, the sensitivity of antigen tests for influenza A was the same as a coin toss. We’re talking about 50%.”

As long as a test is accurate and easy to use, however, the FDA’s data requirements “are not that onerous,” Sharfstein said. The agency is usually able to make a decision about a test months after an application is submitted, he added.

“Tests with high sensitivity and specificity will have no difficulty being cleared by the FDA, but it’s important that the FDA understand how this was determined, what the procedures were, and actually analyze the data,” Sharfstein said.

Mina said she hopes the FDA will authorize a combined home Covid and flu test this month or next, but it might not look like the version in Europe. The test could still involve two separate swabs – one for each virus – that are packaged together, he said.

“The FDA is a little less comfortable putting this fully combined test in people’s homes right away,” Mina said. “I don’t really understand that part. I don’t think there’s good logic behind it.”

But public health experts have not given up hope that a combined rapid test for Covid, flu and RSV will one day reach consumers.

The FDA is “feeling a lot of pressure from Americans,” Mina said. “Americans and now are seeing Europeans having these tests available, and just like with Covid, there is now an effort to say, ‘Why don’t we have this? Why are they not available to us?’ The agency is starting to understand this and is actually willing to work with manufacturers to see them through.”