As the pandemic continues, the Food and Drug Administration has granted extensions to the shelf life of some at-home rapid antigen tests, causing confusion about whether a test is safe to use.
If you find a box of tests that says they’re expired, are they really past their prime? Not necessarily, says Dr. Eli Aronoff-Spencer, an assistant professor of medicine at University of California San Diego who co-leads a NIH grant to develop and commercialize new tests.
Why this matters
COVID-related medical technology is brand new. Confusion around at-home testing kits could lead to waste, or unnecessary spread of the coronavirus.
At-home COVID rapid tests are similar to other tests previously on the market, such as pregnancy tests. They work because of chemical reactions that occur with antigens, proteins found in the novel coronavirus.
It’s important to remember that while the technology of these test kits is not new, the virus is. When test makers took their products to market, they had limited data to show how long they last.
“So when the [Food and Drug Administration] says ‘How long does the test kit last?’ what they’re really saying is ‘How long did the test kit get tested for?’” said Aronoff-Spencer.
“Just like we know milk that’s gone past its spoil date sometimes isn’t spoiled,” he said. “That’s almost certainly the case here.”
The materials in the test kits can degrade, making them less reliable. “It’s usually water, oxygen and heat that are the three biggest enemies,” Aronoff-Spencer said.
But with more time, companies have been able to show that their tests work beyond the printed expiration dates, so it’s worth checking the FDA’s website before throwing them out. The agency has granted extensions for some tests — not all — and you can find an updated expiration date for the brand you have at home.
If you find that the test has indeed expired — or if they’ve been stored for a long time in a hot environment, such as your car — the FDA recommends using a different one.
inewsource is among recent customers confronted with unexpected issues of expired tests.
Carla Sánchez, inewsource’s finance director, recently placed an order for 160 COVID tests through California’s Testing Task Force. She received them in less than two weeks — 20 more than she originally ordered. But when she examined the boxes of iHealth rapid tests, she noticed the boxes they came in said they were all expired.
Sánchez almost tossed them before she noticed a line at the bottom of the emailed order confirmation. “Questions about expiration dates?” it read. She found that the expiration dates for the tests inewsource received had been extended by six months.
“I would have thrown them away,” she said. “There should have been more communication about it.”
In response to questions from inewsource, the state health department said that some people have called about the expired tests, and that information explaining the situation would be made more prominent in future emails.
Expired or not, Aronoff-Spencer urged caution when using home antigen tests.
“They can be very reliable, or they can be somewhat reliable,” Aronoff-Spencer said. “Usually, if they say you’re positive, it’s true.”
But since antigen tests are less sensitive than lab tests — meaning they may not detect an infection even if a person is sick — false negatives are more likely, especially if you test too soon after exposure or if you don’t have symptoms.
“When you’ve got a negative and you’re about to go see someone who could die from COVID, or you’re about to expose a whole bunch of people, be thoughtful,” he said. “Get another test.”