Kids use soft drinks trick to fake Covid positive tests
A range of fluids, from fruit juice to cola, have been used to fool the Covid Lateral Flow tests
Hull: Children are always going to find cunning ways to bunk off school, and the latest trick is to fake a positive Covid-19 lateral flow test (LFT) using soft drinks. So how are fruit juices, cola and devious kids fooling the tests and is there a way to tell a fake positive result from a real one?
Mark Lorch, Professor of Science Communication and Chemistry, University of Hull, cracked open bottles of cola and orange juice, then deposited a few drops directly onto LFTs. Sure enough, a few minutes later, two lines appeared on each test, supposedly indicating the presence of the virus that causes Covid-19.
It’s worth understanding how the tests work. If you open up an LFT device, you’ll find a strip of paper-like material, called nitrocellulose, and a small red pad, hidden under the plastic casing below the T-line. Absorbed to the red pad are antibodies that bind to the Covid-19 virus.
When you do a test, you mix your sample with a liquid buffer solution, ensuring the sample stays at an optimum pH, before dripping it on the strip.
The fluid wicks up the nitrocellulose strip and picks up the gold and antibodies. The latter also bind to the virus, if present. Further up the strip, next to the T (for test), are more antibodies that bind the virus.
But these antibodies are not free to move – they are stuck to the nitrocellulose. As the red smear of gold-labelled antibodies pass this second set of antibodies, these also grab hold of the virus.
The virus is then bound to both sets of antibodies – leaving everything, including the gold, immobilised on a line next to the T on the device, indicating a positive test.
Gold antibodies that haven’t bound to the virus carry on up the strip where they meet a third set of antibodies, not designed to pick up COVID-19, stuck at the C (for control) line. These trap the remaining gold particles, without having to do so via the virus. This final line is used to indicate the test has worked.
Is there then a way to spot a fake positive test? The antibodies (like most proteins) are capable of refolding and regaining their function when they are returned to more favourable conditions. The researcher tried washing a test that had been dripped with cola with buffer solution, and sure enough the immobilised antibodies at the T-line regained normal function and released the gold particles, revealing the true negative result on the test.
(The author is the Professor of Science Communication and Chemistry at University of Hull; theconverstion.com)
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