Is It Flu or COVID-19? At-Home Combination Tests Can Check for Both

It’s that time of year when a fever, sore throat, and stuffy nose could easily signal flu or COVID-19. While at-home tests for SARS-CoV-2, the virus that causes COVID-19, became an important way of detecting coronavirus infections during the pandemic, people may not realize there are also combination tests that check for both SARS-CoV-2 and influenza A and B—typically the most common strains of the flu virus.

Last winter, the Food and Drug Administration (FDA) granted emergency use authorizations (EUAs) for a number of at-home combined flu/COVID-19 tests. This fall, the agency granted the first marketing authorization for another combo flu/COVID-19 test: the Healgen Rapid Check COVID-19/Flu A&B Antigen Test™. The marketing authorization designation signifies that the product has undergone a more thorough review of safety and efficacy while an EUA expedites the availability of medical products during a health emergency.

The combo tests approved last year under EUAs, including Pfizer’s Lucira COVID-19 & Flu Home Test®, can be found online and in pharmacies and typically sell for $25 to $30 for a two-pack. The Healgen test is expected to be available soon for consumer purchase, according to the company.

Scott Roberts, MD, a Yale Medicine infectious diseases specialist, says an at-home combo test is a useful tool—especially because it can facilitate prompt treatment.

“Often, when an individual begins to feel sick, they wait a few days before calling their doctor. And then, the doctor might not have an appointment for two days. By that point, if they have the flu, it is past the window for taking Tamiflu, an antiviral treatment that can lessen symptoms, but it should be started within 48 hours of symptom onset,” Dr. Roberts says. “Similarly, with COVID, treatment with the antiviral therapy Paxlovid should start within five days of symptom onset.”

With access to an at-home test, people can test themselves sooner and call their doctor for a prescription. If they aren’t interested in antiviral therapy or are outside the window of time in which it would be useful, knowing a diagnosis of flu or COVID-19 is helpful in other ways. It can prevent further spread of the illness if they test at home instead of coming into a medical setting—and they also know to stay away from people who are vulnerable to serious illness from flu or COVID-19, including infants, elderly people, and anyone who is immunocompromised.

Below, Dr. Roberts talks more about at-home combo flu/COVID tests.

Similar to at-home COVID-19 tests, a combo test includes a nasal swab that you use to collect a specimen from each nostril. You then dip the swab in a liquid solution, mix it, place drops from the solution in a testing cassette, and wait 15 minutes for results. The test panel will show red or other colored lines, depending on the specific test, for positive results for Flu A, Flu B, and COVID-19.

“For both flu and COVID, I would recommend testing at symptom onset and, if negative, retest in 48 hours,” Dr. Roberts says. “And while someone can have both flu and COVID-19 at the same time, it is rare.”

These tests are for people ages 2 and up. Those 14 and older can test themselves; children 2 to 14 should be tested by an adult.

These are antigen tests, also known as “rapid tests.” Antigen tests tend to be less sensitive than molecular (often a PCR, or polymerase chain reaction) tests, which are processed in laboratories. A test with lower “sensitivity” could mean there’s more of a chance of a false negative result, Dr. Roberts explains.

“My biggest concern would be related to the sampling process. If you don't go far enough back in the nose during the swab, you might have a false negative test result and think you're fine,” he says. “So, I would caution that if it is negative, just be aware you still could have it. The best way to be sure would be to repeat the test 48 hours later.”

But if sampled correctly, the results are very accurate. According to the FDA, the Healgen test correctly identified 99% of negative and 92% of positive samples of SARS-CoV-2 samples; it also identified 99.9% of negative flu A and B samples and 92.5% of positive flu A and B samples.

Comparatively, the Lucira test correctly identified 99.9% of negative and 88.3% of positive COVID-19 samples; it also identified 90% of positive and 99.3% of negative flu A samples. For flu B, which was not widely circulating at the time, it identified 99.9% of negative samples.

In health care settings, providers use what’s called a quad test to check for COVID, flu A, flu B, and RSV (respiratory syncytial virus), a common respiratory virus that infects the nose, throat, and lungs, and can have similar symptoms to flu and COVID-19. An at-home RSV test has not been developed.

Even if you can test at home and start to receive treatment for COVID-19 or flu, Dr. Roberts cautions that if you are extremely ill—for example, if you have trouble breathing—you should seek immediate in-person medical care.