Some see him as a passport to safe parties.
But if the test can help, betting everything on it would be a serious mistake, warn specialists.
Here is what you need to know about screening before Christmas placed under the sign of the health crisis.
Who really has to submit to it?
"Priority to people with symptoms", responds the infectious disease specialist Olivier Bouchaud, head of department at the Avicenne hospital in Bobigny (Seine-Saint-Denis) who recalls that this remains the heart of the strategy to control the epidemic.
"But I know that asymptomatic people ask themselves the question a lot before Christmas," he continues.
I would say that a test is relevant for them if they have people at risk in their entourage and especially - I insist on this point - if they keep in mind that a negative test at the moment T does not want say that they are not going to become potentially infectious afterwards.
"
What is the risk?
"Take the test for a kind of immunity totem," responds immunologist Jacqueline Marvel, using the expression used by the Minister of Health, Olivier Véran.
"Already, a negative test can be a liar, we call that a false negative," she decrypts.
Then, if you've been shopping, taking transportation, hanging out with people before doing so, you can become positive soon after you've had your results.
"
“The natural tendency, and in good faith, is to say to yourself:
My test is negative, it's good, I can relax the barrier gestures.
And there, that can be a real trap, ”adds Professor Bouchaud.
In short: if you are positive, you exclude yourself from parties and isolate yourself so as not to endanger anyone.
If you are negative, you behave exactly as if you could become a contaminant.
VIDEO. Coronavirus: this antigenic testing center gives results in 15 minutes
Which test to choose?
Antigens, which deliver their secret in less than 30 minutes, in pharmacies and in certain medical offices… or the famous PCR, which can be carried out in laboratories?
It is neither the method (both are done by a sample in the nose), nor the price (they are both reimbursed) that should guide the patient, but his state of health.
“PCR is much more sensitive,” recalls researcher Jacqueline Marvel.
The reliability of antigens depends on the amount of virus present.
Clearly, if we have no symptoms, we must opt for the first solution.
If you cough, have a fever, like a bad cold, the second one can make sense.
"Provided that the antigen test is carried out in the first four days following the onset of symptoms", explains Olivier Bouchaud.
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When to do it
“If we opt for PCR, the biological point of view would be to say about 48 hours before the holidays, that is to say the 21st or the 22nd for New Years Eve of the 24. But logistically, can the labs cope with such an influx?
Nothing is less certain… ”, warns Jacqueline Marvel.
For antigenics, we might as well do it "as late as possible", but always applying the sacrosanct rule of not believing yourself to be safe.