Covid expert warns public not to do a lateral flow test in cold weather

7 December 2021, 15:03 | Updated: 7 June 2023, 08:56

An expert on infectious diseases has told the public not to take a lateral flow test in cold weather, warning it could change the results on the test.

Epidemiologist and Immunologist for infectious diseases, Michael Mina, warned people to only use lateral flow tests indoors in places with temperatures over 13 degrees to avoid a false result.

Taking to Twitter, the former Harvard University professor said: "Do not use rapid tests in the cold.

"Using the test in the cold can cause false negatives because the reagents may not bind [to the] virus well or show a line.

"It's ok if your nose is cold and the test is warm. But maybe let your nose warm up a bit too before swabbing."

He advises anyone using a rapid lateral flow test over the festive season to do it before leaving the house or in a car that is above 13 degrees Celsius to avoid a false negative.

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His advice continued: "Also, if your counter or table or wherever you are letting them sit for the 15 minutes is cold - like a granite countertop - place it on top of the box or literally any other surface that's not cold [for example a] wood table, book, etc."

But Mr Mina's cold weather warning does not apply to storage, as lateral flow tests should be stored in slightly cooler locations as heat can "potentially impact their chemistry".

He recommends storing tests below 26 degrees Celsius to avoid false negatives.

His warning comes after the UK government advised Christmas shoppers to conduct lateral flow tests before hitting the high street this month.

A new section on the government's updated coronavirus advice page recommends that people who are spending time in "crowded and enclosed spaces" should take a lateral flow test.

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Official advice now reads: "You are at higher risk of catching or passing on COVID-19 in crowded and enclosed spaces, where there are more people who might be infectious and where there is limited fresh air.

"You may wish to take a rapid lateral flow test if it is expected that there will be a period of high risk that day. This includes spending time in crowded and enclosed spaces, or before visiting people who are at higher risk of severe illness if they get COVID-19."

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This is the first time the government has advised to get a test before heading into a "high-risk" environment with previous advice focusing on getting tested before meeting vulnerable people or twice weekly.

The advice on the Government website says that around one in three people who have Covid-19 do not have any symptoms, which means they could be spreading the virus without knowing.