With so many potential viruses in play, it would be helpful if Americans had a way to distinguish between different ailments at home. And when it comes to the flu in particular, at-home testing could help telehealth doctors decide when it makes sense to prescribe treatments like Tamiflu, which need to be started within two days of onset of symptoms.
“Home flu testing would ensure that those who do need and receive antiviral medication for influenza are the ones who need it the most,” said Christina Yen, an infectious diseases doctor at the University of Texas Southwestern Medical Center, as well as ensure “that we are making our treatment decisions based on data.”
Yet no at-home flu tests are available for purchase in the U.S. That’s not for lack of technology — the rapid antigen flu tests at the doctor’s office are “virtually identical” to the Covid tests already in people’s homes, according to Zoë McLaren, associate professor of public policy at the University of Maryland Baltimore County who studies health policies for infectious disease epidemics.
Rather, the issue comes down to historical hangups — and the need to find digital fixes to address them.
“It’s really rare, and it’s really new, that people are allowed to know about what’s happening inside their body without a physician in the middle,” said Michael Mina, a former assistant professor of epidemiology at Harvard.
The Food and Drug Administration has been historically slow to approve over-the-counter tests, Mina said, citing pregnancy tests as an example. Although a 26-year-old female product designer made a prototype of an at-home version of a lab pregnancy test in 1967, at-home pregnancy tests were not approved in the U.S. until 1977. “The general thinking was, ‘How could a woman possibly know what to do if she found out she was pregnant on her own without a doctor in the room?’ That is a ridiculous concern because women have been doing that for millions of years,” said Mina.
The FDA was similarly cautious with respect to at-home testing for HIV, which became the only over-the-counter test for an infectious disease when it received approval in 2012.
A 2016 FDA advisory panel, meanwhile, was split on whether the benefits of over-the-counter influenza tests outweighed the risks. Meeting transcripts show that as experts debated whether at-home tests would actually be effective at keeping people at home if they knew they or their children had the flu, one panelist joked that daycare centers might make the decision for parents if over-the-counter tests were available.
“The woman is going to want to go to work, and she wants to drop her kids off at daycare,” the panelist said. “The daycare, when they sign their contract, [could say] ‘If your kid has symptoms, we’re going to test him,’” and send the child home if they tested positive.
The room laughed at the idea.
This scenario is not so laughable in the wake of the pandemic. During the height of the Omicron wave, nearly 1 in 4 symptomatic people were testing themselves at home. Many Americans have clearly gotten accustomed to the idea of at-home testing, and to the fact that they may have to adjust their plans if they get a positive result.
But regulators and clinicians still have concerns. At-home tests can be less accurate than tests administered by a health care worker because people may not obtain enough sample to get a valid result, or might have trouble reading the result correctly. And whereas home users generally take a positive or negative result at face value, clinicians have more context with which to interpret false positives or false negatives. They might order a more sensitive test, act with more caution for people they know are high-risk, or decide to treat a patient anyway because they suspect a false negative.
There’s also a historical concern about rapid influenza tests having low accuracy and varying in sensitivity from year to year. Before 2009, measuring viruses by cell culture was the decades-old standard — but cell culture numbers could vary widely depending on how good the lab was at cultivating cells.
During the 2009 H1N1 pandemic, nucleic acid amplification tests such as PCR — which were much more consistent — became the new standard. When compared against PCR methods, rapid-antigen flu tests now seemed much less reliable than they had been when their cell-culture-based trials were first approved.
Based on outcry from the medical community against rapid flu tests so inaccurate that some were only able to detect H1N1 in 11% of samples, the FDA in 2017 reclassified antigen influenza tests from Class I devices to Class II, which are considered to present more risk. The FDA began requiring manufacturers to certify their tests against eight influenza strains, which change from year to year depending on circulating variants. These year-to-year fluctuations can become a concern if people keep flu tests in their medicine cabinets and pull them out months or years later.
There may be ways to address concerns about patients inaccurately administering and interpreting at-home tests. eMed, where Mina is currently chief scientific officer, is trying to address such issues by having a telehealth professional proctor each at-home test the company sells.
But while the eMed tests are marketed as at-home flu and Covid tests, the kits only contain a FlowFlex rapid Covid test. Because there isn’t an approved at-home flu test, clinicians can’t ask the patient to test for flu like they would if they were in person. Instead, they follow the Centers for Disease Control and Prevention guidance for diagnosing flu through telehealth. If the patient is Covid-negative during flu season, for example, they probably have the flu, and clinicians might then decide to prescribe Tamiflu. But this set-up can prompt telehealth clinicians to over-prescribe antivirals, as Yen at UT Southwestern pointed out.
This situation is particularly frustrating because there are rapid flu tests that are Clinical Laboratory Improvement Amendments-waived, meaning they are approved for use in point-of-care testing sites like pharmacies and health clinics—just not at home.
“It’s kind of like [the FDA] still lives in a world where the internet and telehealth doesn’t exist,” said Mina. “There are ways to get people testing at home that don’t require the person to be in charge of interpreting the results all on their own.” He imagines a scenario in which the FDA could broaden access to diagnostic tests by making telehealth appointments a CLIA-waived setting, so that patients could swab their own noses under the guidance of a health-care provider.
Whether the FDA would support that kind of change is unclear, though a senior FDA official said that the agency is currently trying to find a better way to bridge point-of-care and at-home approvals.
The senior official also said that the administration “strongly supports” at-home tests for respiratory viruses and has since before the pandemic. But companies developing these tests have gotten a different impression from their interactions with the FDA. “I’m glad to hear they said that,” said Wade Stevenson, a senior vice president of marketing at rapid-PCR test manufacturer Visby Medical.
Stevenson acknowledged that the FDA has a hard job — they’re trying to safeguard the products available to the American medical system without stifling innovation. “When you put a new idea in front of the FDA, generally, they’re excited about it,” said Stevenson. “They like to see new ideas. And they do not want to play the role of, ‘No, this is never going to work.’ They want to encourage development and people pushing boundaries.”
But manufacturers are frustrated about what they say is a lack of clarity surrounding the pathways to approval for over-the-counter tests and constantly shifting goalposts.
One obstacle manufacturers like Visby face is the question of what the FDA is looking for in the at-home tests. The FDA has strongly emphasized they want test manufacturers to engage with them by submitting pre-submissions for feedback. But Stevenson said that the FDA’s guidance for their pre-submissions came back too late to be useful for developing their clinical trials. Clinical trials take a long time to complete because the prevalence of flu, especially low-incidence influenza B, has been so fickle the last few years.
Stevenson thinks a Visby at-home PCR test is “a long ways away,” partially because the latest suggestions the company received from the FDA specified that the administration would like public health reporting to be built into at-home tests. This would help address the problem facing Covid tests today, where the reported case counts don’t include unreported at-home tests. But including this feature is “not trivial” because each state has its own reporting standards and different ways they collect that data.
“The FDA saying ‘Think about this’ is nice and has good intentions,” said Stevenson, “but the reality is coming up with one product that does that today in an at-home setting? I don’t know how to do that.”
Beyond getting tests approved, it’s hard for test makers to transition into the at-home market because insurance reimbursements don’t typically cover at-home tests, whereas lab diagnostics are usually covered. In 2020, Congress required insurers to cover Covid tests at no cost, but that stipulation only lasts while the national public health emergency is in place. And while at-home tests are ostensibly meant to help lower barriers to access medical care, CDC research shows that the people most likely to use an at-home Covid test are highly educated, in higher income brackets, and white — meaning that if and when at-home flu tests are approved, there’s more work to be done in ensuring they actually reach all populations.
Currently, the only test available for differentiating flu, Covid, and RSV at home is the Labcorp Pixel test, where users swab themselves at home and send the sample in for lab testing. However, this test’s turnaround time of one to two days wouldn’t be able to compete with an at-home test that gave results in 15-30 minutes.
Some Covid test manufacturers are now pivoting to include flu in their analytes. Cue Health and Lucira Health have both filed emergency use authorizations for their Covid and flu at-home tests, both of which are molecular-based amplification tests and thus might sidestep some of the sensitivity concerns of antigen tests. Both companies also have a companion app that can help connect patients to treatment options like Paxlovid or, if approved for flu, Tamiflu. However, neither have yet been approved by the FDA. Lucira’s test, which has been authorized in Canada and Europe, was submitted for authorization in May, while Cue Health’s request was submitted at the end of September.
“We are in constant communication with the FDA,” said Debkishore Mitra, founder and CTO of Lucira. “We are really hoping that we can make some impact in this current flu season.”