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Coronavirus: an American test, praised by Donald Trump, would produce up to 48% of false results

2020-05-13T22:12:06.843Z


This high rate of false negatives "makes this technology unacceptable in our clinical environment," conclude the study authors.


Will Donald Trump have to be tested again? Rapid test for Covid-19, touted by the President and used daily in the White House, produces between a third and a half of false negative results, according to a preliminary study by researchers at New York University (NYU).

The test, which produced positive results in 5 minutes and negative results in 13 minutes, was compared to those of another slower machine. When the rapid test sample was diluted in a culture medium (a transport liquid), it missed a third of the samples confirmed positive by the other machine.

This rate rose to 48% when the cotton swab remained dry, which is however the method recommended by the Abbott laboratories which designed this rapid test.

The researchers pre-published their comparison on the public site biorxiv.org, where thousands of researchers put their studies online while waiting for their evaluation by a scientific journal.

The Langone medical center in NYU wanted to verify the accuracy of the new test because it would have greatly accelerated the screening of patients arriving in the emergency room and suspected of being infected with the new coronavirus Sars-Cov-2. Its advantage is that it is done on site, in a small machine called ID NOW, without the need to send the samples to a laboratory.

Reduced efficiency on small samples

By comparison, the molecular test (PCR) of the pharmaceutical group Roche gives results in three and a half hours, and that of Cepheid 45 minutes. To detect the presence of the virus in a sample (taken from the nose, the back of the nose or the throat), these tests try to "photocopy" on a large scale the piece of virus that interests them, in order to make it visible.

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It turns out that Abbott's test, according to this comparative study, is relatively reliable when it announces a positive result. However, its effectiveness apparently decreases quickly when the amount of virus in the initial sample decreases. Consequence: the test misses many positive results.

This high rate of false negatives "makes this technology unacceptable in our clinical environment", conclude the authors. On March 30, the American president himself presented Abbott's machine, which weighs about 3 kg and the size of a toaster, to the White House.

An Abbott spokesperson responded that the results were "not consistent" with those of other studies, and stated that "the rate of false negatives reported to Abbott was 0.02%", without further details . "It is not known whether the samples were tested properly in this study," added the spokesperson.

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Source: leparis

All news articles on 2020-05-13

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