On the same day that the Centers for Disease Control and Prevention eased COVID-19 guidelines, the Food and Drug Administration issued a statement warning that at-home rapid antigen tests can deliver false negative results and people who need tests should should plan to do so more than once to make sure they are not “unknowingly spreading the SARS-CoV-2 virus to others.”
Health experts recommend tests for people who have been exposed to the virus or are experiencing symptoms.
“Today’s recommendations are based on the latest study results from people with likely Omicron infection showing that repeat testing after a negative at-home COVID-19 antigen test result increases the chance of an accurate result,” the FDA said, via safety communication released on Thursday.
Previously, the FDA had advised people to conduct two rapid antigen tests over two or three days to rule out infection.
These recommendations, the FDA said, are based on data from a comprehensive study conducted in collaboration with the National Institutes of Health (NIH) and the University of Massachusetts Chan Medical School, which showed that this method of testing repeatedly reduced the risk of negative results. The study is said to have included more than 7,000 participants.
In the warning, the agency said that antigen tests, also known as COVID-19 at-home tests, are less accurate than molecular tests, such as polymerase chain reaction (PCR) tests. This means that taking an at-home test too early, after being exposed to COVID-19 could lead to a false-negative result, particularly if a person has no symptoms.
The FDA now advises that people who plan to use at-home tests get several of them so they can test more than once. For people with COVID-19 symptoms who test at home and receive a negative result, the agency recommends taking a second at-home COVID-19 test, 48 hours after the first, for a total of at least two tests.
“If you get a negative result on the second test and you are concerned that you could have COVID-19, you may choose to test again 48 hours after the second test, consider getting a laboratory molecular-based test, or call your health care provider,” the FDA said.
For those who suspect a COVID-19 exposure but have no symptoms, the FDA now recommends up to three tests, each separated by a 48-hour period.
If a person tests positive at home initially or after repeating a test, the agency emphasized that this likely means a person has COVID-19 and he or she “should follow the CDC guidance for people with COVID-19.”
Health experts have cautioned that testing too early can lead to false negative results. For those who have been exposed to COVID-19, the Centers for Disease Control and Prevention recommends waiting at least five days after being exposed to COVID-19 before taking an antigen test. The reason for this is that it can take several days for these at-home tests to detect an infection.
The FDA also said that people don’t need to stick to one specific test brand, and can use tests from different manufacturers each time for this repeated testing approach. A list of all FDA-authorized home tests and more information about at-home COVID-19 testing, can be found here.