Should You Use an Expired COVID Test? The Answer Might Surprise You

Should You Use an Expired COVID Test? The Answer Might Surprise You

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COVID-19 has been a part of life for nearly four years now and, with new variants like EG.5, or “Eris,” and BA.2.86, or “Pirola” popping up, it shows no signs of going away any time soon. But what about those at-home COVID tests that have been on your shelf collecting dust? Do expired COVID tests work?

Here’s the thing: They can expire and there is COVID test expiration date printed on your package that you may not even realize is there.

Many COVID-19 tests last for just a year or so, but the odds are high that you’ll need to use your test at some point. That may or may not be before the expiration date stamped on your package passes.

With an uptick in COVID-19 cases, hospitalizations, and deaths, it’s understandable to start thinking about testing again—and if the ones you’ve had for a while are still good.

So…do expired COVID tests work, or do you need to toss what you thought was a perfectly good test? It’s actually a little complicated. Here’s what you need to know.

So, do expired COVID tests work?

Yes and no. To fully understand that, it’s important to explain how COVID-19 tests get an expiration date in the first place. “When tests are developed, the company will assess the test over time to make sure it’s performing with the quality standards intended,” says Thomas Russo, M.D., a professor and the chief of infectious diseases at the University at Buffalo in New York. “Whatever time frame they assess it for is the expiration date that will go on that test.”

This “doesn’t necessarily mean that the test won’t perform for a longer period of time,” Dr. Russo says—it’s just the amount of time that the test has been assessed for and what is authorized or approved by the Food and Drug Administration (FDA).

Older tests are more likely to have shorter expiration dates because there were time pressures to get tests out earlier in the pandemic when home tests were first developed, and only so much time since they had been created to test how long they were good for, Dr. Russo says. “However, companies kept assessing the tests over time,” he says.

As a result, “many manufacturers have received shelf life extensions by the FDA,” says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security.

The FDA has a list online of authorized home COVID-19 tests, along with links to “updated expiration dates” so you can check to see if your test’s expiration date has been extended.

“If you have a test and it’s ‘expired’ based on what the package says, it may or may not be the most correct expiration date,” Dr. Russo says.

What happens if you use an expired test?

Again, the expiration dates are a reflection of how long the company that manufactured the test found that it was good for—or the period of time in which they were able to assess the test. With that, there’s a chance that your test will still be good beyond the expiration date listed. “Most tests will still perform past their expiration date for several weeks,” Dr. Adalja says.

Why do COVID tests expire?

COVID tests contain specific reagents (a.k.a. ingredients) that react with the virus, or lack thereof, from your swab, explains Jamie Alan, Ph.D., associate professor of pharmacology and toxicology at Michigan State University. “These ingredients do not work forever,” she says. “This is true for medications, lab materials, and food.”

Can an expired COVID test show a false positive?

It’s possible for an expired COVID test to show a false positive—but it’s also possible for a non-expired COVID test to show a false positive, Dr. Russo says. It’s just not super likely. “It’s more likely that you’d get a false negative,” he says.

Alan agrees. “The test might be negative because the reagents or ‘ingredients’ are past their shelf life and are not working as they should,” she says. “They are likely good past their expiration date, although how long I cannot say with any degree of certainty.”

“If an individual has symptoms consistent with COVID and they test positive, they should assume they have COVID,” Dr. Russo says. But if you happen to get a positive test result and you don’t have symptoms of the virus, he suggests waiting a day and testing yourself again—or calling your doctor about getting a PCR test, which is considered the gold standard of COVID-19 testing.

“I’m much more concerned about false negatives,” Dr. Russo says.

Keep in mind that when home COVID-19 tests were first released, many had accuracy levels around 80%—and some brands cited even higher numbers. But a recent small study from Caltech University now suggests that home COVID-19 tests are only about 44% accurate.

That study analyzed data from 17 people with COVID-19 and tracked when the virus appeared in their throat, saliva, and nose, along with when home COVID tests were able to detect the virus.

The researchers found that the virus appeared in the throat or saliva several days before it appeared in the nose, which is what most home COVID-19 tests swab. Nearly 90% of study participants also had high levels of the virus in their bodies for at least a day before they received a positive result on their home COVID-19 test, the researchers found.

But research has also found that home COVID-19 tests provide accurate results when someone has symptoms of the virus. A scientific analysis published in The BMJ in 2021 notes that these tests “produce very few false positive results” and a lot of the accuracy surrounding them depends on factors like how well you collect a sample and how it’s processed. “Despite their limitations, their ability to provide near instantaneous results avoids the delays associated with PCR and facilitates timely isolation of the most infectious cases and their close contacts, who may otherwise transmit infection while waiting for a PCR result,” the researchers wrote.

Whether you opt for a PCR or antigen test, testing remains important to curb the spread of COVID.

Do old COVID tests work for new variants?

There’s been a lot of concern about COVID-19 tests working on new variants like “Eris” and “Pirola,” but Dr. Russo says there’s no reason to suspect your old tests wouldn’t pick up these strains of the virus—if they’re not expired.

“Eris” and “Pirola” are still new variants, with EG.5 becoming the most common COVID-19 variant in the U.S. just late last month. As a result, there isn’t a lot of data yet on how well these home COVID-19 tests perform on them.

Still, Dr. Russo isn’t concerned. “The tests aren’t based on the spike protein, which has the greatest number of changes between variants,” he says. “Instead, they’re based on the nucleocapsid antigen.” There are some changes to this protein in the newer variants, but it’s thought that home COVID-19 tests should still be accurate with them, Dr. Russo says.

“But if you have symptoms consistent with COVID-19 and your test is negative, you should test again in a day or two,” Dr. Russo says.

How do I know if my BinaxNOW is expired?

BinaxNOW is one of the most popular home tests out there, and it typically has an expiration date stamped on the back of the box. But, again, that may not be the most up-to-date expiration date for your test.

If you have a test with an expired date on the package, check out the FDA’s list of updated expiration dates for BinaxNOW tests to see if it’s been extended. Just keep in mind that you’ll need to have your box’s lot number handy.

But, if your test is expired—both on the box and per the FDA’s updated dating—and you want to be sure you’re getting an accurate reading, Dr. Russo says it’s “probably best to not use that test.” Instead, opt for a PCR or grab an alternative home test.

This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.

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