If you're confused about why you're consistently testing negative on your at-home antigen test even though you're experiencing Covid symptoms, you're not the only one.
More and more people are reporting that their at-home tests are coming back negative even with what are clear symptoms of Covid-19—fever, fatigue, muscle aches, loss of taste and/or smell—and experts are investigating if BA.5's mutation is the reason.
Cases of BA.5 and BA.4, are taking a little bit longer to appear positive with antigen testing for some folks, according to Esther Babady, chief of the clinical microbiology service at Memorial Sloan Kettering Cancer Center in New York.
"As mutation occurs, it may somehow change the structure of these different proteins, which may result in a decrease in detection by the antigen testing," says Babady. "It can also be that earlier in the infection by BA.4 and BA.5, you don't produce enough of the SARS-CoV-2 protein."
While experts work to pinpoint the exact cause and its relation to the new variant, other possibilities linger.
It could also be the brand of the test being used that's causing the negative results, according to Babady.
"The challenge in trying to make one statement for all the rapid antigen tests is that there are so many already on the market, and they're not all equal," Babady says, "So, when we say this is not working, it might also be related to a particular brand."
But at this time, infectious disease experts have not concluded that antigen testing cannot detect BA.5, and it is too early to make that claim, according to Mohamed Z. Satti, an infectious disease specialist and faculty member in the division of public health at Michigan State University.
Satti believes that people should still use at-home antigen tests if they're experiencing symptoms or have been exposed to someone with Covid. "Until now, from all the data I'm seeing, the home testing is still working and sensitive enough to depend on," Satti says. "People should still continue to do at-home testing."
According to a recent study in medRxiv, in the pre-print stage, there isn't a significant difference between the accuracy of at-home antigen tests at detecting the omicron variant compared to its accuracy detecting delta.
With this in mind, Satti points to yet another possible cause of the prevalence of negative results: inaccurate application of at-home antigen tests. Medical professionals are more skilled at administering testing than the average person, and false negatives may be due to improper handling of the test by people at home, he says.
In addition to the testing you're doing at home, consider getting a PCR test done if you have access to one. PCR tests have always been more sensitive than antigen testing, says Babady, and are a great option if you're worried about the accuracy your at-home-test's results.
You can search for your local testing locations by using the Department of Health and Human Services' community-based testing site locator for Covid-19, which list the options for your state. Alternatively, the Covid-19 testing locators provided by CVS, Walgreens or Rite Aid are great tools for setting up testing appointments.
"If someone has a high suspicion of having BA.5 and their antigen test is negative, a PCR test will really rule it out," says Babady.
If you can't get a PCR test, test multiple times with at-home antigen tests over multiple days, according to Kevin Dieckhaus, chief of the division of infectious diseases at UConn Health. Many people already take multiple tests to confirm test results, but give thought to testing three times over three days, with 24 hours in between each test, if symptoms persist, Dieckhaus says.
"Classically, it was you had to have two tests over 24 hours that were negative before you'd really believe it," he says, "I've heard some discussion that maybe more testing over a longer period of time would be needed before you truly believe it."
It's important to consider the possibility that you could just have a common cold or be experiencing allergies. In the U.S., allergies affect more than 50 million people per year, according to the American College of Allergy, Asthma and Immunology. In recent months, experts are also seeing cases of the flu and other respiratory viruses that are typically more common in the winter.
Regardless of your test results, if you're experiencing Covid-like symptoms, Babady recommends isolating if you can and masking indoors around others. Even mild symptoms can manifest into severe symptoms for someone else, especially if they're more at risk than you are, she notes.
"We are still in a time where the most likely explanation for a respiratory infection is SARS-CoV-2," says Babady. "Even if it's not [Covid], you don't want to transmit another virus to someone else."
This article has been updated to correctly refer to the Department of Health and Human Services.