A post on Facebook claims that a small amount of Heinz tomato ketchup tested positive for Covid-19 using a lateral flow test.
This is inaccurate. We have seen, and reported on, a number of similar self-styled experiments with food including oranges, Coca-Cola and kiwi fruit before.
In reality these items don’t test positive, they break the test completely. The fact the tests react this way with food and drink doesn’t mean they are unsuitable for use by the general population.
Dr Alexander Edwards, associate professor in Biomedical Technology at the University of Reading, previously told Full Fact on this subject: “If you completely ignore the manufacturer’s instructions or in fact use the test for something completely different, then you shouldn’t really be surprised if you get a silly result.”
As we have recently reported, a review of 64 studies published in March found that the average value for how well the tests were able to pick up positive Covid-19 cases (the sensitivity, or how many “true positives” it detects) was 69%.
Meanwhile Public Health England (PHE) evaluations from November show lateral flow tests are 99.68% specific. In this context, specificity means how successful the test is in correctly detecting people without Covid-19.