This is the moment a NHS doctor with 4.6 million TikTok followers explains why antigen tests can throw up false positives with fizzy drinks and even tap water.
Dr Karan Rangarajan, better known as Dr Karan Rajan, is an NHS surgeon and lecturer at the University of Sunderland who also boasts 4.6 million followers on TikTok.
Outside of his medical work, Dr Rajan uses his social media platform to entertain and teach others about health matters.
He was asked by a follower why their lateral flow test showed positive after it was splashed with ordinary tap water.
In the footage, viewed over 6 million times, Dr Rajan apparently carries out the same tap water test on a lateral flow device that then shows up positive.
While lifting the cover off the test, he says: “First we need to look inside the lateral flow device.”
He adds: “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.”
In November, the American Society for Microbiology pointed out the importance of carrying out the test correctly, saying that “a team of Canadian researchers has shown that rapid antigen tests for SARS-CoV-2 work only when manufacturer instructions are followed”.