With so many potential viruses at play, it would be helpful if Americans had a way to differentiate between different ailments at home. And when it comes to the flu in particular, home tests can help doctors decide when it makes sense to prescribe treatments like Tamiflu, which should be started within two days of the onset of symptoms.
“Home flu testing would help ensure that those who need and receive antiviral medication for flu are the ones who need it most,” said Christina Yen, an infectious disease physician at the University of Texas Southwestern Medical Center, and ensures ” that we make our treatment decisions based on data.”
Yet there are no home flu tests for sale in the US. 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, said Zoë McLaren, associate professor of public policy at the University of Maryland, Baltimore County, who health policy for infectious disease epidemics.
Rather, the problem boils down to historical hangups – and the need to find digital solutions to address them.
“It’s really rare, and it’s really new, that people are allowed to know what’s going on in their bodies without a doctor in the middle,” said Michael Mina, a former assistant professor of epidemiology at Harvard.
TThe Food and Drug Administration has historically been slow to approve over-the-counter tests, Mina said, citing pregnancy tests as an example. Although a 26-year-old female product designer prototyped a home version of a lab pregnancy test in 1967, home pregnancy tests in the US were not approved until 1977. Does a woman know what to do if she finds out she’s pregnant on her own, with no doctor in the room?’ That’s ridiculous, because women have been doing that for millions of years,” says Mina.
The FDA was similarly cautious about home testing for HIV, which became the only over-the-counter test for an infectious disease when it was approved in 2012.
A 2016 FDA advisory panel, meanwhile, was divided on whether the benefits of over-the-counter flu tests outweigh the risks. Meeting transcripts show that while experts debated whether home testing would really be effective in keeping people home if they knew they or their children had the flu, one panelist joked that daycare centers could make the decision for parents if over-the-counter testing was available.
“The woman is eager to go to work and she wants to drop her kids off at daycare,” said the panelist. “The childcare, when they sign their contract, [could say] “If your child has symptoms, we’re going to test them,” and send the child home if they tested positive.
The audience laughed at the idea.
This scenario is not so laughable in the aftermath of the pandemic. At the peak of the Omicron wave, nearly 1 in 4 people with symptoms tested themselves at home. Many Americans have clearly become accustomed to the idea of 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. Home tests may be less accurate than tests performed by a health professional because people may not get enough sample to get a valid result, or they may have trouble reading the result correctly. And while home users generally take a positive or negative result for granted, clinicians have more context to interpret false positives or false negatives. They may order a more sensitive test, act more cautiously for people they know are at high risk, or decide to treat a patient anyway because they suspect a false negative.
There is also a historical concern about rapid flu tests with low accuracy and varying sensitivity from year to year. Before 2009, measuring viruses through cell culture was the decades-old standard, but the number of cell cultures could vary widely depending on how good the lab was at growing cells.
During the 2009 H1N1 pandemic, nucleic acid amplification tests such as PCR – which were much more consistent – became the new standard. Compared to PCR methods, rapid flu antigen tests now seemed much less reliable than they had been when their cell culture-based studies were first approved.
Based on the medical community’s outcry against rapid flu tests that were so inaccurate that some could only detect H1N1 in 11% of samples, in 2017 the FDA reclassified flu antigen tests from Class I devices to Class II, which are considered more risks. The FDA began requiring manufacturers to certify their tests against eight flu strains, which change from year to year depending on the circulating variants. These year-to-year fluctuations can become a concern if people keep flu tests in their medicine cabinets and take them out months or years later.
There may be ways to address concerns about patients taking and interpreting home tests inaccurately. eMed, where Mina is currently Chief Scientific Officer, is trying to address such issues by having a professional telehealth invigilator for every home test the company sells.
But while the eMed tests are marketed as home flu and Covid tests, the kits only contain a FlowFlex rapid Covid test. Because there is no approved home flu test, clinicians cannot ask the patient to test for flu as they would if they were in person. Instead, they follow the Centers for Disease Control and Prevention’s guidelines for diagnosing the flu through telehealth. For example, if the patient is Covid-negative during flu season, they probably have the flu and clinicians may decide to prescribe Tamiflu. But this set-up can push telehealth clinicians to overprescribe antivirals, as UT Southwestern’s Yen pointed out.
This situation is particularly frustrating because there are rapid flu tests that have had their clinical lab improvement amendments waived, meaning they’re approved for use in point-of-care testing locations like pharmacies and health clinics — just not at home.
“It’s kind of like [the FDA] still lives in a world where internet and telehealth do not exist,” says Mina. “There are ways to get people to test at home where the person isn’t just in charge of interpreting the results.” He envisions a scenario where the FDA could broaden access to diagnostic testing by making telehealth appointments a CLIA waiver, allowing patients to wipe their own noses under the guidance of a healthcare provider.
Whether the FDA would support that kind of change is unclear, though a senior FDA official said the agency is currently trying to find a better way to bridge point-of-care and home approvals.
The senior official also said the administration “strongly supports” home testing for respiratory viruses and has done so even before the pandemic. But companies developing these tests have taken on a different impression through their interactions with the FDA. “I’m glad to hear they said so,” said Wade Stevenson, senior vice president of marketing at Visby Medical, manufacturer of rapid PCR tests.
Stevenson acknowledged that the FDA has a tough job – they try to protect the products available to the US medical system without hindering innovation. “When you present a new idea to the FDA, they’re generally excited about it,” says Stevenson. “They like to see new ideas. And they don’t want to play the role of, “No, this is never going to work.” They want to stimulate development and push people’s boundaries.”
But manufacturers are frustrated with what they say is a lack of clarity on the paths to approval for over-the-counter testing and constantly shifting goalposts.
One obstacle manufacturers like Visby face is the question of what the FDA is looking for in the home tests. The FDA has strongly emphasized that they want test manufacturers to work with them by submitting pre-submissions for feedback. But Stevenson said the FDA’s guidelines 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, particularly low-incidence influenza B, has been so volatile in recent years.
Stevenson thinks a Visby home PCR test is “still a long way off,” in part because the latest suggestions the company received from the FDA specified that the administration would want public health reporting built into home tests. This would help address the problem Covid testing is facing today where reported cases do not include unreported home testing. 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 well-intentioned,” Stevenson said, “but the reality comes with one product that does that today in a home setting? I don’t know how to do that.”
BBefore tests are approved, it is difficult for test makers to transition to the home market because insurance reimbursements typically do not cover home tests, while lab diagnostics are usually covered. In 2020, Congress required insurers to cover Covid testing at no cost, but that provision only applies while the national public health emergency is in effect. And while home testing is ostensibly designed to lower barriers to accessing medical care, CDC research shows that the people most likely to use a home Covid test are highly educated, higher-income, and white — which means if and when home flu tests are approved, there is more work to be done to ensure they actually reach all populations.
Currently, the Labcorp Pixel test is the only test available to differentiate between flu, Covid and RSV at home, with users taking a swab at home and sending the sample for lab testing. However, this test’s one to two day turnaround time would not compete with a home test that gave results in 15-30 minutes.
Some Covid test manufacturers are now working to include flu in their analytes. Cue Health and Lucira Health have both filed emergency use authorizations for their home Covid and flu tests, both of which are molecular-based amplification tests and thus can circumvent some of the sensitivity issues of antigen testing. 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 has yet been approved by the FDA. Lucira’s test, which is approved in Canada and Europe, was submitted for approval in May, while Cue Health’s request was filed in late September.
“We are in constant contact with the FDA,” said Debkishore Mitra, founder and CTO of Lucira. “We really hope we can make some impact in this current flu season.”