Coronavirus: with antigenic tests, "we will let cases pass"

INTERVIEW

The Ministry of Health paved the way on Saturday for a large deployment of antigenic tests to detect Covid-19, by issuing an order authorizing their reimbursement for symptomatic people.

Like RT-PCR tests, this screening method is performed by taking a sample from the nostrils.

But when a PCR test requires laboratory analysis for the virus's genetic material, the antigenic test detects the virus's protein in 30 minutes.

Faster screening of course, but less reliable alerts Jean-Claude Azoulay, vice-president of the National Union of Biological Physicians, on Europe 1. 

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Precautions to be taken, even in the event of negative tests 

"The High Authority for Health had already issued a favorable opinion on October 9 in order to use them for symptomatic patients. Extending them to other uses is a little more questionable: the test is not sufficiently sensitive in my opinion. So, putting it in airports, that can pose a problem ", explains the medical biologist.

"You should know that the test is positive when the patient carries a large number of viruses on him, since it is a test which will detect the virus protein, unlike the PCR which will amplify the genome of the virus. So there is has precautions to take. Positive patients, it is certain that they are quite positive. On the other hand, at the level of the negatives, we will let cases pass. "

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By the end of the month, antigenic tests will be generalized in airports, announced Jean-Baptiste Djebbari, Minister for Transport.

Until now, antigenic tests were only allowed in the context of collective screening operations, people with symptoms were excluded, and their result had to be confirmed by an RT-PCR test.

If Jean-Claude Azoulay understands the government's decision to facilitate passenger traffic, he calls for caution.

"From the moment the patient has a test, even negative, he must wear his mask very seriously in the flight. Avoid removing it, that we do not serve food, no drink, so so that there is no possibility for these patients who are moderately positive to contaminate their neighborhood, "lists the vice-president of the National Union of Biological Physicians.

"I think we should continue to do PCR tests and use antigen tests when travelers really have not been able to get tested, or when there is a stopover."

These antigenic tests are now extended to individual screening and can be carried out by nurses, pharmacists or doctors, under certain conditions: patients under 65 years old, no risk of serious forms, symptomatic people only if an RT PCR test cannot be obtained before 48 hours and if the antigen test takes place less than four days after the first symptoms, for example. 

Improved lead times for RT-PCR tests

Thus, in the immediate future, the antigen test will not be able to replace the RT-PCR test, neither in the efficiency, nor in the possibility of mass testing, indicates Jean-Claude Azoulay, who however hopes for the arrival of more sensitive tests. .

“Of course there are rapid PCR tests, but they cost a lot more and it's also unitary. It also lasts 20 minutes and it's extremely precise. You can only do a few at a time. not do 230,000 tests per day in rapid tests. It's impossible. If I had 500 tests to do with ten technicians, they would have to work four hours continuously! "

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The vice-president of the National Union of Biological Physicians, however, wants to be confident and notes an improvement in screening in France, especially on time.

"The results are returned in 24 to 48 hours, and sometimes even less than 24 hours in some cases, when it is very urgent," he says.

"We get there by prioritizing and that's why we find a lot of positive. We prioritize those who are likely to be positive so that these people agree to confine themselves afterwards."