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.
In the United States, people wanted to know how to buy the rapid test pictured, which simultaneously screened people for three common respiratory viruses: Covid, respiratory syncytial virus (RSV) and two types of influenza, A and B.
The viruses have circulated widely this winter and share many of the same symptoms, meaning they are often indistinguishable without diagnostic testing. But unlike Covid tests, which are available without a prescription, RSV and flu tests must be done in a doctor’s office or ordered with a prescription. And the FDA has not authorized an at-home test that can quickly detect all three viruses at once.
The Brus photo rapid test is however 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 provider that sells the test online. The test costs 6.5 euros ($6.92) and the company has sold around 10,000 so far, Brus said.
The test’s maker, Shenzhen Microprofit Biotech Co. Ltd., says it captures 100% of negative cases for Covid, influenza or RSV – meaning it won’t produce false positives – and detects 90% of influenza B cases, 92% of influenza A cases, 93% of Covid cases and 95% of RSV cases.
Brus said this performance should be enough to get clearance in the United States
“A test carried out in Amsterdam, where I come from, will give exactly the same result as a test carried out 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 does not plan to seek emergency authorization for its test in the United States. Tang said in an email that he did not believe the Food and Drug Administration would grant clearance, given its regulatory constraints.
Dr Susan Butler-Wu, associate professor of clinical pathology at the University of Southern California, said rapid tests for multiple viruses are “the way of the future” and would help more people access the right treatments. But the United States has historically lagged behind Europe in terms of licensing new diagnostics, she said.
“It’s not uncommon to see things that have been approved in other countries that are great products and we don’t have them here. It’s just the reality of the situation,” she said. “It takes time to go through the process and get approval.”
The FDA has authorized a non-prescription test that allows people to dab for flu, Covid and RSV simultaneously, but the swab must be mailed to Labcorp. The test costs $169 for people without insurance.
The FDA said it strongly supports home testing for respiratory viruses, including combination testing for flu and Covid. But the agency declined to say whether it had received or was evaluating requests for such tests from manufacturers.
“When the data is strong, the FDA has not been shy about moving quickly to authorize testing, with home testing in all areas being a high priority for the agency,” an FDA spokesperson said.
The agency, however, pointed to a hurdle: Home flu tests have traditionally required people to dab high in their noses, which usually means a clinician must administer them.
Unlike Covid tests, Butler-Wu said, there have been fewer opportunities to study whether rapid flu tests can be administered to 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 actually benefit from the test,” said Joshua Sharfstein, a former FDA deputy commissioner who is now a professor of health policy and management at the University. ‘Johns Hopkins University.
Dr. Michael Mina, scientific director of 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 show people can properly administer the tests at home — a process that can cost millions of dollars and delay test approval for months or years, Mina said.
“It took a very long time in the past to get new self-tests allowed, like HIV tests or even pregnancy tests,” he said. “They’ve taken years and years and years and years. We have a pretty conservative regulatory approach.”
In real life, Mina isn’t worried about the user-friendliness of combined tests for respiratory viruses.
“We know Americans can dab their noses because it’s been done millions and millions and millions and millions of times now for Covid,” he said.
Even if a doctor administers a rapid test, the FDA may still have reservations about its accuracy. Butler-Wu said rapid flu tests administered by healthcare professionals are typically about 60% sensitive, meaning they produce false negatives about 40% of the time. For RSV, that performance is “a bit better,” but still unreliable, she said.
“There are long-standing issues with the performance of antigen tests for influenza and RSV that have been extremely well documented,” Butler-Wu said. “In 2009, when the new H1N1 appeared, the sensitivity of antigen tests for influenza A was the same as a pickaxe. We are talking about 50%.”
As long as a test is accurate and easy to use, the FDA’s data requirements “are not that onerous,” Sharfstein said. The agency is usually able to make a decision about a test within months of submitting an application, he added.
“Tests with high sensitivity and specificity will have no difficulty getting FDA approval, but it’s important for the FDA to understand how it was determined, what the procedures were, and actually look at the data,” said Sharfstein.
Mina said he hopes the FDA will allow a combined Covid and flu test at home 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 – which are packaged together, he said.
“The FDA is a little less comfortable getting this fully combined test into people’s homes immediately,” Mina said. “I don’t really understand that part. I don’t think there’s any good logic behind it.”
But public health experts have not given up hope that a combined rapid test for Covid, influenza and RSV will one day reach consumers.
The FDA “feels a lot of pressure from Americans,” Mina said. “Americans and Europeans are now seeing these tests available and, just like in Covid, there is now a push to say, ‘Why don’t we have them? Why are they not available to us? The agency is starting to understand that and is actually somewhat willing to work with manufacturers to see it through.”