Antigen tests don’t like the cold. The health authorities were already alerting a year ago and they are recalling it as the number of anti-Covid-19 screenings explode. These tests exposed to too low a temperature, from less than two degrees, can generate a series of false positives. In question: the delicate chemical reaction when we pour the diluent on the small cassette which tells us if we are sick.
Covid-19: pharmacists warn of test results distorted by the cold. Winnie Claret’s report
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In the middle of winter, this risk exists, especially since many French people go to be tested in pharmacy barnums set up in the street. To talk about it, hood on his head, his feet glued to the small auxiliary heating, Alan waits for the patients under one of the two large white tents installed on the Place du Trocadéro, in the 16th arrondissement of Paris, tight against his colleague . “Here, we are very cold! For example, over there, it’s my tent, but since we only have a heater, so I went with it here” he admits.
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The 18-year-old tester started a week ago. He was trained for two hours by the medical center that hires him. “In truth, it’s silly. We just have to stick a cotton swab in our nose and wait for the result. Afterwards, we send it to the nurse and he sends the result by e-mail to the patients.” says Alan.
No health professional on site: the medical center which manages its barnums is six kilometers away. And the tests remain all day in the cold, at the risk, therefore, of distorting the results and generating false positives.
Practically different in this pharmacy of the 15th: a shed is just in front of the dispensary. Diamanta, a pharmacy student, constantly goes back and forth.
“We go straight back and bring them inside so that the results are as reliable as possible.”
Diamanta, pharmacy studentat franceinfo
Apart from the swab, diluent and screening cassette remain inside. No question of compromising the tests. “When we are responsible, we are responsible from A to Z. We really have to communicate the fairest result.” defends for his part the pharmacist Laurent Halwani.
️ Covid-19: are the tests carried out in the cold really reliable? The explanations of Lionel Barrand, president of the National Union “Medical Biologists”, on franceinfo pic.twitter.com/Ss3yitbIAs
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So to avoid any error, the union of community pharmacists calls on the State to increase checks on wild barnums and also recalls that the self-tests are also sensitive to the cold and that they must be left at room temperature. It is therefore necessary to avoid leaving them in your car trunk with particularly cool temperatures at the moment, for example.
On franceinfo, Lionel Barrand, president of the National Union “Les Biologistes Médicales” (Les Biomed), thus recalls that the self-tests are to be “used well” and to be read after the statutory 15 minutes. But more broadly, they should not be used as PCRs: “It’s a test that only detects high viral loads. So we have performance below 44% sensitivity in people without symptoms and we probably have out of 10 infected people 7 or 8 who will be falsely negative with self-test“, warns Lionel Barrand.