Can I use an at-home test for COVID-19 that has been snubbed?

key takeaways

  • Rapid tests at home should continue to work if they are placed in freezing temperatures for a short period of time.
  • Bringing the test back to room temperature for at least two hours should work, but heat exposure may damage it and make it unusable.
  • When in doubt, check that the control wires under test are properly displayed according to the test instructions. If not, the test may be flawed.

As parts of the North and Southeast experience cold snaps and snow, the federal government is mailing COVID-19 tests to households across the country.

Most home tests authorized by the U.S. Food and Drug Administration (FDA) should be stored at 35 degrees or higher. Below this temperature, the test liquid will freeze, possibly reducing its effectiveness.

According to the FDA, COVID-19 test manufacturers take into account weather changes and often provide a range of acceptable temperatures on test packaging. Testing should be performed in an environment around 59-86 degrees Fahrenheit.

“Because shipping conditions can vary, test developers perform stability testing to ensure that test performance remains stable when stored at different temperatures, including summer shipping in very hot regions and winter shipping in very cold regions ,” the FDA said.

For example, the BinaxNow test should be stored at 35.6-86 degrees, while Ellume says it stores its quick test at 59-95 degrees. Both must be used at room temperature.

How does temperature affect testing?

The longer the test is outdoors and the cooler the temperature, the more likely it is to freeze or lose some of its efficacy. It’s best to bring the package in as soon as it arrives. If it’s cold outside, let the unopened test sit inside for at least two hours until it reaches room temperature, according to the FDA.

“If it’s sitting outside and you’re in Alaska or the Northwest — it’s very cold there — and it’s been freezing for days, it could be affected,” said Michael Blaivas, MD, emergency physician and chief medical officer at Anavasi , FACEP, FAIUM diagnosis, tell VigorTip. “If you’re somewhere in the country, let’s say it dropped to 35 degrees yesterday and it didn’t get cold after the carrier put it down, just let it warm up to room temperature, there really shouldn’t be any issues.”

On the other hand, tests exposed to high temperatures can be irreversibly damaged. Just as eggs harden and jelly liquefies under heat, proteins in antigen tests break down or change form.

In a study of 11 commercially available antigen tests, researchers found that storage at 98 degrees produced false negatives, while storage at 39 degrees had a greater risk of false positives.

“When the temperature is too high, you can basically inactivate all the key active ingredients,” Braiwas said. “Then you get a false negative test.”

He said high temperatures were the “bigger enemy” of the active ingredient in these tests, not freezing temperatures. The longer the test is left in a hot environment, the greater the chance that the ingredients will break down. While this may not be a problem for many Americans in the winter, placing the test in a warm location, such as near a space heater, may affect its effectiveness.

Should you still use tests?

The best way to check if your test is broken is to make sure the “control” line is still showing as expected.

Make sure the liquid reagent in the test is not frozen when used. You can simply feel the container – if it’s cold to the touch, wait a little longer. Results may be inaccurate if the test leads do not appear in the correct location or within the time described in the instructions. Better to do a new test.

“If it’s been in the cold overnight and doesn’t freeze too much, as soon as the control line comes in, I’m more confident that that’s an indicator that the test will be good,” Braiwas said.

The instruction booklet that accompanies the exam will detail the appropriate conditions for taking the exam. While designed to be used at home, these rapid antigen tests are adapted from more sophisticated lab tests, with little margin for error, Blaivas said.

A good rule of thumb for testing throughout the pandemic also applies here – trust a positive result. False positives are far less common than false negative results. Also, extreme weather that damages the test is more likely to destroy the sensitivity of the test, which means you’re more likely to get false negatives.

A professional review of the efficacy of the BinaxNOW test found that those using tests below the recommended range of 46-58.5 degrees detected only two-thirds of positive cases.

“If you’re sitting in a hotspot and you’re having symptoms and you’re feeling really bad, and everyone in your family has Covid-19 and you test negative, you really can’t believe that,” Braiwas said. Molecular testing is needed.”

If you have symptoms of COVID-19 and get a negative result from a rapid test, it is best to follow up with a more sensitive PCR test to confirm your infection status.

If there is a problem with testing for COVID-19, you can report the incident through the MedWatch Online Voluntary Reporting Form.

what does this mean to you

To avoid damaging your rapid antigen tests, experts recommend storing and using them at room temperature. If the test has been placed in the cold, allow it to return to room temperature by leaving it unopened for at least two hours before use.

The information in this article is current as of the date listed, which means that you may have updated information as you read this article. For the latest updates on COVID-19, visit our Coronavirus news page.