Doctor explains how tap water and fizzy drinks can give false positives on Covid tests

NHS doctor Dr Rajan, who is best known for dispelling health myths on TikTok, has revealed why substances like tap water and fizzy drinks can produce false positives on antigen Covid tests

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Lateral flow test shows tap water tests positive for Covid-19

Ever since lateral flow antigen tests became available for the wider public to test for Covid-19, there have been stories of people using tap water, fizzy drinks and even fruit juice, to bring up false positives on the test.

Some conspiracy theorists have used this to try and falsely argue that the pandemic is a hoax, or that there are actually far fewer cases than being reported.

Of course, this is not the case, and in actual fact it’s very easy to bring up a false positive if the tests aren’t used in the way designed to do so.

NHS doctor Dr Karan Rangarajan, who is known as Dr Rajan on TikTok, recently took to the app to explain exactly why this happens, after being questioned by a follower.

Dr Rajan took to TikTok to explain how antigen tests work



The tests only work when used properly



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In a clip which has since been viewed more than six million times, Dr Rajan, who regularly debunks health myths on TikTok, could be seen splashing tap water on the antigen test before bringing up a positive result.

“First we need to look inside the lateral flow device,” he said, before lifting the front casing off the test. “This grey box and the portion just above it contain antibodies that are sensitive to the COVID-19 virus.

“If you use things like soda, tap water and fizzy drinks, that’s going to provide an altered pH, which will affect the function of the antibodies on the test line.

“That is why you need to use this buffer solution (consisting of 99.7 percent saline solution) which provides a stable pH that will actually make the test work.”

So there we have it – the antigen tests will only work if we use them the way they’re supposed to be used – who’d have thought it?

Luckily, Dr Rajan’s explanation was backed up by the American Society for Microbiology, back in November, confirming that “a team of Canadian researchers has shown that rapid antigen tests for SARS-CoV-2 work only when manufacturer instructions are followed.”

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