The countdown begins at fifteen minutes.
But it will take less than one for the rectangle-shaped device to reveal its secrets.
In exactly 50 seconds, two lines turn purple.
No doubt, the lady to whom the sample belongs is positive for the coronavirus.
"Normally, it takes longer but there, the viral load is so high that the result is immediate", comments Nazim Hanou, engineer at the Henri-Mondor hospital in Créteil (Val-de-Marne), who leaves everything behind. even a quarter of an hour goes by, as a precaution.
In the basement of the establishment, it is in this reference laboratory that the performance of several antigenic tests (exactly six, two of which are stored) were evaluated.
Antigene-what?
If the French are now used to the famous PCR screenings that invite themselves into their nostrils, they will have to familiarize themselves with this new tool for detecting the virus in the body.
Expected for their conclusions faster than the PCR - a handful of minutes against several hours, even days - antigenic tests take off in France.
They will be deployed next week at Paris airports.
In pharmacies, nurses or general practitioners, in mid-November, according to the schedule announced by Olivier Véran to our colleagues at Les Echos.
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“Antigenics is certainly not a Copernican revolution, but it is far from trivial.
It will allow a real turning point, ”we confirm at the Ministry of Health.
Strengthening testing capacities: an emergency because the virus does not wait to get away.
Nearly 30,000 new patients every day, crossing the 34,000 death mark.
This Thursday, the Prime Minister was clear: "November will be trying", with hospitalizations and deaths.
Laboratories are taken by storm with some 1.6 million tests carried out in a week.
Overcrowding and galloping epidemic, so many elements which undoubtedly explain why the Ministry of Health went, it is rare enough to underline it, beyond the recommendations of the High Authority of Health (HAS).
On October 9, the latter considered that there was "no place", for lack of real benefit, to carry out antigenic screening "not targeted, in the general population.
However, it is decided, the individual screening will take place, but only if a PCR test cannot be obtained before 48 hours and if it takes place less than four days after the first symptoms.
Only 60% sensitivity, but ...
If PCR remains the reference, it is because the antigen is less reliable: only 60%.
“But the more contagious we are, the more sensitivity increases.
It will be 93 to 95% if we test at the beginning of the disease, with symptoms.
Certainly, we will miss some cases, but they will be the least contagious ”, specifies Professor Jean-Michel Pawlotsky, virologist and head of the biology center at Mondor.
As he did with 412 medical students, he believes that the method is tailored for massive screenings.
“It may seem counterintuitive to you, but the goal is to identify the negatives,” he continues, “to focus on the positives properly.
The confirmation PCR, which was initially mentioned, is however no longer relevant.
Bad news for the patients, in both cases: the sample is always nasopharyngeal, with the introduction of the swab into the nose!
It is the analysis technique of the two tests that differs (and their price, the antigen is cheaper).
For PCR, the genetic material of the virus is searched for after an amplification step.
For the antigen, we try to detect its proteins.
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To understand, we return to a few meters from his office, in the laboratory where Nazim Hanou put on a gown, double pair of gloves and FFP2 mask.
Under the hood, he takes a small amount of the sample to put it in an extraction liquid.
"That's it, the virus is destroyed, it will release its constituents, proteins that we are going to question", launches the engineer.
The interrogation takes place on the adjoining bench.
The researcher opens a “Rapid test” sachet, takes out a white cassette on which he places a few drops of his mixture.
Kind of like a pregnancy test.
There, the antibodies interact, the protein is trapped, the strip shows red.
If the patient had been negative, she would have remained colorless.
In the process of running in on site, the antigenic tests will land "by the end of the month" at the Paris airports of Orly and Roissy.
“They are already accepted for overseas destinations,” Groupe ADP tells us.
Other destinations could benefit from it, but the country of arrival must recognize their validity.
The strip shows red bands, much like a pregnancy test.
If the patient had been negative, she would have remained colorless./LP/Aurélie Ladet
The technique is also being tested in nursing homes.
"Ultra-practical", enthuses Jacques Finielz, the director of the Protestant retirement home in Montpellier (Hérault) where the 91 residents and 70 members of staff were tested.
100% negatives.
Three days before, we had celebrated Georgette's 100 springs there.
“If the antigen had already been there, we would have known within fifteen minutes if the guests were infected and we could have loosened or strengthened the measures accordingly.
"And the owner of nursing home to launch an idea:" Rather than closing nightclubs, why not offer this test at the entrance?
"
Today, 14 antigenic kits are eligible for reimbursement.
Next step and not the least, their arrival in pharmacies, doctors and nurses.
"It is a great challenge that we will take up," says Carine Wolf-Thal, president of the Order of Pharmacists.
Staff must be trained in nasopharyngeal swabbing, set up Covid circuits, all during the flu vaccination period.
Will all pharmacists be able to test?
"92% vaccinate, that wants them to have the appropriate premises", she points out.
“We are dealing with a real public health issue.
We must unite all our forces to avoid re-containment.
It goes through a solid testing system.
"