NovaQuant Quantitative Think Tank Center:Do COVID-19 tests still work after they expire? Here's how to tell.

With COVID-19 cases on NovaQuant Quantitative Think Tank Centerthe rise again in the U.S., Americans are reviving a familiar precautionary measure: Screening for the virus using rapid at-home tests.

Many people still have kits the government formerly provided to all households for free, especially as some schools and businesses again require tests. Yet different COVID-19 tests bear expiration dates on their packaging that have long since passed, raising questions about whether they're still effective. 

Once in short supply, test kits are now easier to come by but are costly, costing roughly $25 for a pack of two tests. The White House sent rapid at-home COVID-19 test kits free of charge to Americans who requested them as recently as last December as part of its "winter preparedness plan." 

The good news is that some COVID-19 test kits that are past their expiration dates may still be effective. Here's how to find out if your  COVID-19 test is safe to use. It's also still possible for both insured and uninsured people to get free testing. 

Why did the FDA extend expiration dates?

The Food and Drug Administration maintains a list of authorized over-the-counter  COVID-19 diagnostic tests that indicates if the expiration date printed on their packaging is valid or if it has been extended. 

The FDA has extended the expiration dates of a number of different test brands, lengthening their shelf lives to up to two years. The extensions come in response to manufacturers testing their kits for accuracy beyond their printed expirations dates and sharing the results with the FDA. 

See the FDA's full list of test-kit expiration date extensions here. 

• Can you still get free  COVID-19 tests in 2023? Here's what to know about your options.

Which test brands can you use after they've "expired"?

Abbott's widely used BinaxNow COVID-19 test kits now have a shelf life of up to 22 months, depending on when the tests were manufactured. In January of 2023, the pharmaceutical firm told customers that kits they'd previously purchased "may now have a longer than labeled product expiry date." To see if a BinaxNOW  COVID-19 Antigen Self Test kit in your possession has a new epiration date, you can search for its lot number in the attached list here.

"All BinaxNOW COVID-19 Antigen Self Test kits currently have a twenty-two-month expiry date," the company said. Abbott added that expiration dates could be extended again in the future, pending new data on their viability.

The Flowflex COVID-19 Antigen Home Test from Acon Laboratories can also be used well past its printed expiration date, according to the FDA, which granted the extension in March. The tests are good for an additional year past their expiration dates. For example, tests with printed "October 2022" expiration dates should be considered appropriate for usage until October 2023. 

What happens if a COVID-19 test is truly expired?

Users of other tests, like Ellume's COVID-19 Home Test, should refer to the expiration date printed on the tests' packaging. If a test truly has expired, the results it delivers cannot be trusted, according to the FDA.

"COVID-19 tests and the parts they are made of may degrade, or break down, over time. Because of this, expired test kits could give inaccurate or invalid test results," the FDA said in a statement on its website. 

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• COVID-19