A group of UK students used orange juice to falsify Covid-19 test results after discovering that using the drink in lateral flow tests, the so-called rapid tests, could generate a false positive, according to the British newspaper ‘The Guardian’.
The phenomenon seems to be linked to the acidity of the orange juice, which, according to the newspaper, undoes the test result. The same effect was also seen in several other foods and beverages, including ketchup and Coca-Cola.
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A UK science teacher said his students showed the effect. “They say it’s a great way to take two weeks off from school,” he said, quoted by ‘The Guardian’.
Andrea Sella, an expert at University College London, said the finding was not surprising. “If someone deliberately messes up the protocol, then of course we’re going to get a false result. But I would add that it is not a ‘false positive’ in the true sense. Because false positives are those that arise despite adherence to the protocol”, he explained.
The “trick” also appeared on TikTok, with videos of people trying out different liquids. There have been over 6.5 million views of videos uploaded to the social network with the search hastag ‘#fakecovidtest’ (fake Covid test).
Jon Deeks, professor of biostatistics at the University of Birmingham, criticized the practice. “False positives affect not just that child, but their family and their bubble at school, it’s a very selfish thing to do. There are less harmful ways to fake a day off from school,” he said.
In turn, Mark Lorch, professor of science communication and chemistry at the University of Hull, said it was possible to detect a “false” positive test by washing it with a buffer solution that restores the device to the correct pH. After this process, the “positive” line in a false test disappears, revealing the negative result.
While the falsification of rapid positive tests may cause concern, not least because everyone must immediately isolate themselves, the interruption may be short-lived: anyone with a positive test must subsequently have a PCR test to confirm an infection.
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