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Will your COVID-19 tests freeze in the mailbox?

USPS began delivering free at-home tests to many states in freezing climates.
Posted at 10:11 PM, Feb 03, 2022
and last updated 2022-02-03 23:11:04-05

GREEN BAY, Wis. (NBC 26) — Americans are starting to receive the free at-home COVID-19 rapid tests they ordered from a federal program earlier this year, but are noticing some parameters on the box that state tests should not be kept below freezing temperatures. Here in Wisconsin, it is usually below 32°F this time of year, even at the warmest part of the day.

The FDA has acknowledged that "test performance may be impacted if the test is used while it is still cold, such as being used outdoors in freezing temperatures or being used immediately after being brought inside from freezing temperatures." So how can users ensure an accurate test result?

When first asked about this issue on Thursday, state DHS officials had no answer and deferred to federal authorities.

"It's a fair point," Chief Medical Officer and state epidemiologist Ryan Westergaard said in a press conference. "It's likely if they're in a mailbox then they'll be in cold temperatures. But what the strategy to mitigate that, since it was a federal program, we need to hear from them."

Experts say the truth is unknown and that officially, nobody knows if the cold would impact the test results. That is why the guidelines are in place to protect the tested performance barometers.

"What that means is the test may or may not perform exactly the way that the manufacturer designed them to perform," Dr. Jeff Pothof, Chief Quality Officer of UW Health said. "It doesn't mean that the test won't work or it'll always give a positive or always give a negative. But it just means we don't know."

According to the FDA, bringing a test inside your home to warm up to room temperature for at least two hours should provide appropriate conditions to perform as accurate of a reading as possible. If lines appear in the correct place in the correct time period, it is safe to assume the test is accurate. If not, the FDA recommends other testing avenues.

FDA guidelines on tests left in the cold

Dr. Pothof believes that delivering this many tests for free to the American people may not have been as cost-effective if they included climate-controlled delivery.

"I almost think you can use them as if they didn't freeze. We should try to stop them from freezing," Dr. Pothof said. "If they do, it's not game over. But continue to use these rapid tests in the way they were designed for, which is maybe turn positive a little bit later, and you may just want to wait or confirm with a PCR."