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How to properly store your at-home COVID-19 rapid tests in cold weather

Temperature changes — including extreme heat and cold — may affect results.

We're heading into our third winter holiday season amid the COVID-19 pandemic, so it makes sense to have some home rapid tests on hand to keep your gatherings as safe as possible. But storing those rapid tests improperly might give you inaccurate results.

If you store them in a part of your home that's too warm, or if the tests are exposed to extreme temperatures during shipping, the results might not be reliable, experts told TODAY. In particular, warmer temperatures can permanently damage the tests and give false-negative results, meaning the test will say you're negative when you actually have COVID-19.

With updated COVID-19 boosters available, experts say we're likely to have better protection against the omicron subvariants that are circulating now. But, knowing that we've seen surges in coronavirus cases for the past two winters, experts think it's likely we'll see another one this year. That's why it's more important than ever to be able to rely on the results you get from COVID-19 tests.

Here's what you need to know about storing and taking the tests to get the most accurate results possible — and help protect your community.

Get the tests inside as soon as possible

Exposure to extreme hot or cold temperatures may affect the accuracy of home COVID-19 rapid tests, Dr. Amy Mathers, associate professor of medicine and pathology and associate director of clinical microbiology at the University of Virginia School of Medicine, told TODAY.

After exposure to very high temperatures, components of the reagent chemicals that come with the test may be permanently damaged in a way that affects the sensitivity of the test, Mathers said. "When you cook an egg, it denatures the proteins," she explained. "In this test are proteins that are going to be very sensitive to becoming too hot."

At colder temperatures, the test may still be temporarily affected. But it will generally still be usable as long as the liquids in the test kit don't freeze, she said. "If you warm them back up to room temperature when you run them, they do seem to work quite well." 

But, ultimately, both hot and cold temperatures can affect how well the tests work in sometimes unpredictable ways, Omai Garner, Ph.D., associate clinical professor and director of clinical microbiology at UCLA Health, told TODAY.

Although each brand of at-home test may be slightly different, they’re all meant to be kept within a specific range of temperatures, Garner said. In general, you should try to keep the tests between 35 and 86 degrees, he explained. “The box shouldn’t get outside of those temperatures — even temporarily,” he explained.

So if you ordered the tests online, you should try to bring them inside your home as quickly as possible rather than letting the delivery sit out in the sun. And if you picked them up at the store, you shouldn’t leave them in the trunk of your freezing car overnight, for example.

Related: Still testing positive for COVID-19 after 10 days? Here’s what to know

Store them in an area of your home that stays at room temperature

Knowing that temperature may reduce their accuracy, you should be careful where you decide to store COVID-19 rapid tests in your home.

“Put it away in a dry, room-temperature location,” Dr. Emily Volk, president of the College of American Pathologists, told TODAY.

Avoid storing the tests in an area that isn't temperature-controlled, such as an unheated garage or basement. You also shouldn't keep your home COVID-19 tests in a part of your home that experiences changes in temperature, like in a bathroom cupboard that might get warm and humid when you take a steamy shower or on a kitchen counter that could be exposed to heat from an oven.

Check for any potential damage to the test kit

When you receive your home COVID-19 tests, check the box for any damage the test might have sustained during shipping, though damage to the box itself "isn't a big deal," Garner said, "because it's really all about the reagents that are inside that box."

And while even the packages of reagents "should be pretty durable from physical stressors," Mathers said, you don't want to see any leaking. If you do, you shouldn't use the test.

Likewise, if you open the box and notice that any components of the test kit have come unwrapped or gotten torn or wet, don't use the test, the experts said.

Related: Is a faint line on a COVID-19 test actually positive?

Read through the instructions before storing and taking the test

Just because you've taken one type of rapid test, don't assume you know how they all work. There may be some differences in instructions, so check the box when you receive a test for the exact storage and usage guidelines for that particular brand of test.

When it's time to take your test, read the instructions all the way through and plan to devote your full attention to the process. "You're performing a clinical laboratory test on your kitchen table," Volk said. "Turn off your cell phone, and have somebody else answer the door."

Take the test — and interpret your results — according to the specific instructions on the box

“These are medical tests,” Mathers said. “They’re developed for use in medical settings by trained personnel. So you really, really need to follow the instructions to the exact letter.”

That means it's important to keep the temperature in mind here, as well: "The range of temperatures to run the test is actually much more narrow," Garner explained, adding that most tests work best when the temperature is between 65 and 86 degrees.

So you shouldn't use the tests outside, say, before entering an event in cold or hot weather. Or if your COVID-19 test was exposed to cold temperatures, you should let it warm up to room temperature before using it, Mathers said.

Garner also shared a warning about one of the most common rapid test mistakes he's seen: "The most common mistake that I've seen is not reading the results within the appropriate time frame," he said.

If your test instructions tell you to wait 15 to 30 minutes, you should only consider the results that appear within that time frame to be accurate.

Reading the results too soon may turn up a false-negative result because the test didn't have time to properly process your sample, Garner said. And reading the results too late may give you a false-positive result. "If you wait an hour, you may see a faint line there, but that doesn't mean it's real," he explained.

And don't forget the larger context of why you're taking the test when interpreting your results, Volk urged. If you have symptoms consistent with COVID-19 and you've been in high-risk situations recently, but your rapid test comes back negative, "you might want to get another more sensitive test," like a PCR test, she said.