More and more people are reporting that their tests at home are coming back negative even with obvious symptoms of Covid-19 — fever, fatigue, muscle aches, loss of taste and/or smell — and experts are investigating whether BA.5’s mutation is to blame.
Cases of BA.5 and BA.4 take a little longer to show positive with the antigen test for some people, according to Esther Papadi, chief of the clinical microbiology service at Memorial Sloan Kettering Cancer Center in New York.
“When the mutation occurs, it may somehow change the structure of these different proteins, which may lead to a decrease in detection by antigen testing,” says Papadi. “It could also be that, earlier in infection with BA.4 and BA.5, you do not produce enough SARS-CoV-2 protein.”
Here’s what you should know
While experts work to determine the exact cause and its relationship to the new variant, other possibilities remain.
According to Papadi, it may be the brand of the test used that is causing the negative results.
“The challenge in trying to make a single statement for all of the rapid antigen tests is that there are already a lot on the market, and they are not all equal,” says Papadi, “so when we say this doesn’t work, it may also be associated with a particular brand.”
But at this time, infectious disease experts have not concluded that an antigen test cannot detect BA.5, and it is too early to make that claim, according to Muhammad Z. at Michigan State University.
Sati believes that people should continue to use antigen tests at home if they have symptoms or have been exposed to someone with Covid. “So far, from all the data I’m seeing, the home test still works and is sensitive enough to rely on,” Sati says. “People should continue to take the tests at home.”
According to a recent study in medRxiv, in preprint, there is no significant difference between the accuracy of home antigen tests in detecting an omicron variant compared to their accuracy in detecting delta.
With this in mind, Sati points to another possible reason for the prevalence of negative results: the inaccurate application of antigen tests at home. Medical professionals are more skilled at performing the test than the average person, and false negatives may be due to improper handling of the test by people at home, he says.
What to do if the test is negative but you still feel sick
In addition to the test you do at home, consider getting a PCR test if you have access to one. PCR tests have always been more sensitive than the antigen test, says Papadi, and they’re a great option if you’re concerned about the accuracy of your at-home test results.
You can search for your local testing sites using the Department of Human Health’s Community Testing Locator for Covid-19, which lists options for your state. Alternatively, Covid-19 test locators provided by CVS, Walgreens or Rite Aid are great tools for preparing test appointments.
“If someone has a high suspicion of having BA.5 and their antigen test is negative, the PCR test will really rule it out,” says Papadi.
If you can’t get a PCR test, get tested several times with at-home antigen tests over the course of several days, according to Kevin Dichhaus, chief of infectious diseases at UConn Health. Dieckhaus says that many people already undergo multiple tests to confirm test results, but consider testing three times over three days, with 24 hours between each test, if symptoms persist.
“Traditionally you would have had two tests in 24 hours that were negative before you really believed it,” he says.
It’s important to consider the possibility that you may have a cold or an allergy. In the United States, allergies affect more than 50 million people annually, according to the American College of Allergy, Asthma, and Immunology. In recent months, experts are also seeing cases of influenza and other respiratory viruses that are usually more common in the winter.
Regardless of the test results, if you develop symptoms similar to those of Covid, Babdy recommends isolating if you can and hiding others indoors. She notes that even mild symptoms can manifest in someone else’s severe symptoms, especially if they are more at risk than you.
“We are still at a time when the most likely explanation for respiratory infection is SARS-CoV-2,” says Papadi. “Even if it isn’t [Covid]You don’t want to pass on another virus to another person.”
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