When it comes to the coronavirus, many people have given up on testing. Who knows if the box of COVID tests on your shelf will even work, right?

Now there is some new evidence that they do. Recent research from Johns Hopkins Medicine, the University of Maryland School of Medicine and others shows that those rapid antigen tests reliably found positives and negatives whether administered at home or in a doctor’s office.

They were approximately 84% to 88% effective at registering positives in samples taken at a Baltimore testing site in 2022 using the Abbott’s BinaxNOW COVID-19 test.

“We believe this is an important finding because it suggests physicians can feel confident prescribing treatment based on patient-reported, self-administered tests with positive results,” said Dr. Zishan Siddiqui, assistant professor of medicine in the Johns Hopkins University School of Medicine and a team leader of the study.

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They are not close to 100% accurate at detecting the virus like lab-performed PCR tests. PCR tests rely on spotting genetic material as opposed to a protein in the virus like the antigen tests, but Siddiqui said doctors can rely on the results, and they’re so convenient that they have a definite edge when mass testing and regular testing is needed.

And since you probably have a box on the shelf, maybe it’s worth using, so you can take care of yourself and protect others.

Cases are trending down after peaking again in January, but there are still plenty of people vulnerable to severe illness and death, and a small number of people will have persistent illness, known as long COVID. You also have a narrow window yourself to get an antiviral medication such as Paxlovid, which must be taken within a few days of infection.

If you’re reluctant to test for COVID-19 because you don’t want to stay home from school or work, consider this news from The Washington Post: The U.S. Centers for Disease Control and Prevention may issue new guidance this spring saying people without a fever for 24 hours who have mild and improving symptoms don’t have to isolate.

Here are some other things to know about testing, according to Siddiqui:

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Don’t throw away old tests: Many expiration dates on tests have been extended as manufacturers showed evidence they still work. You can check to see if they are still good here.

The U.S. Food and Drug Administration advises against using tests beyond their expirations because the tests can degrade and can give you false negative results.

But Siddiqui says the control line offers some reassurance the test still works, though there are other chemical reactions in those tests that may fail. He said just don’t go too far beyond the expiration date (not a year, maybe months), and double-check a negative result with a second test.

Test on day 4: This study suggests it’s around the fourth day of symptoms that you have peak viral load, making it optimal for testing.

If you don’t have symptoms, the CDC recommends waiting until the fifth day after exposure to test and test more than once if it’s negative.

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If you do have symptoms, you can test when you notice you’re sick. But again, test once more after 48 hours if it’s negative, Siddiqui said.

Order free tests: You can still order four free at-home rapid tests from the federal government here.

Meredith Cohn is a health and medicine reporter for The Baltimore Banner, covering the latest research, public health developments and other news. She has been covering the beat in Baltimore for more than two decades.

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