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Covid-19: rapid antigenic tests are finally available


“The use of antigenic diagnostic tests must be able to be carried out on a large scale outside biological laboratories”, launched in its note of October 26 the Scientific Council. It’s done: these new rapid tests (results in 15 to 30 minutes) can finally be performed by city caregivers, without a prescription. They are arriving in pharmacies and being gradually delivered to the caregivers responsible for carrying them out. In total, some 600,000 professionals (nurses, laboratory assistants, pharmacists, doctors, students, physiotherapists, etc.) have the right to take the sample, but only doctors, nurses and pharmacists can interpret the result and deliver it to the patient. Companies will be able to buy tests and offer them to their employees via the occupational physician, indicates the new health protocol, but no results can be communicated to the employer.

Like PCRs, antigen tests indicate whether the patient is infected at the time of testing. They are faster and cheaper (excluding sampling, € 8.05 excl.tax against € 54 for a PCR analysis). The results are, however, less reliable. This is why the Haute Autorité de santé has reserved its use for two types of public: asymptomatic people (excluding contact cases), for example as part of a large-scale screening carried out within a risk of contamination (university, slaughterhouses, etc.). And the symptomatic, if and only if the result of a PCR cannot be available within 48 hours. The test should then be performed within 4 days of the onset of symptoms. For patients at risk of severe disease (over 65 years of age and / or comorbid), a negative result must be confirmed by PCR. “The antigen test is less sensitive (there is a significant risk of not detecting the virus, editor’s note) as the benchmark test. For people at risk and contact cases, it is imperative to avoid false negatives, and direct them to an RT PCR! ”, explains Carine Wolf-Thal, president of the National Council of the Order of Pharmacists. Antigen testing will help unclog biology labs, but are not meant to replace PCR. “It is absolutely necessary that the authorities communicate clearly on this subject. Antigen tests are not “the silver bullet” ”, recently alerted the Union of Biologists.

Another pitfall: as for PCR, the test is performed from a nasopharyngeal sample. The professional must therefore learn this technical gesture, but above all the logistics are heavy. “These are potentially infected patients so we must wear a gown, mask, charlotte, gloves, explains Sophie Mouilleron, liberal nurse in Nantes who has been taking samples sent to the laboratory since the spring. Even though I’m used to it, it takes me 5 to 10 minutes longer. You also have to disinfect everything afterwards. ”

In the office, this requires a dedicated room or time slot to protect other patients. “All my colleagues will not do it”, indicates the nurse. “In a week to ten days, the pharmacies that will offer these tests will be organized, in particular with the creation of a small room or barnum for the sampling, and personnel trained to take the samples. But not all pharmacies will offer them ”, adds Carine Wolf-Thal. To these difficulties, doctors add that they generally avoid bringing infected patients into their offices …

“The demand is strong”

The tests will be delivered free of charge to health professionals. As for the remuneration, they vary (26 € for the pharmacist if he performs the sample himself, 19 € for the nurse as part of a collective screening and between 26 and 30 € for an individual test carried out at his office. or at home, € 46 for a doctor as part of a consultation). “It is not a lucrative remuneration for pharmacists, given the investments to be made and the half hour spent for each test”, regrets Carine Wolf-Thal. Sophie Mouilleron is rather satisfied, with a reservation for home samples: “The result takes 20 to 30 minutes to appear. Will we have to wait with the patient, or come back to give him the document attesting to the result? ”

A negative test is not a driving license nor a reason to forget the barrier gestures

Carine Wolf-Thal, President of the National Council of Pharmacists

Another unknown, the feedback of results for epidemiological monitoring. The decree of October 17 conditioned in particular the invoicing “The recording of all the information requested in the SI-DEP”, secure platform where all PCR test results are recorded. But for the moment it is only accessible to doctors and biologists. While waiting for it to be open to other health professionals (this should be the case around November 9, hopes Carine Wolf-Thal), a secure email address or, failing that, a telephone number, will allow the results to be communicated to the Cnam which will take care of the ascent.

The French seem enthusiastic: “Demand has been strong for a few weeks”, remarks a pharmacist. At the large Chaussée-d’Antin pharmacy in Paris, the manager indicates that he has “Received 100 this morning and we will immediately recommend 300 because even if things calmed down this weekend, before confinement we had 30 to 40 requests per day”. One of his colleagues plans to devote “A room currently used for orthopedics and flu shots, which can be sufficiently ventilated. The only thing that we haven’t organized yet is how we will do if there is a queue… ” Some have already given up for lack of space, others are waiting “To see if it’s reliable, and not too complicated”. Carine Wolf-Thal slips a warning to patients: “A negative test is not a driving license nor a reason to forget the barrier gestures. You must continue to monitor your symptoms, protect yourself and those around you. ”

A significant risk of not detecting the virus

Among the 24 antigenic tests authorized in France, only 6 have been the subject of an independent evaluation. Among the tests acquired by pharmacies, for themselves or on behalf of nurses and doctors, that of the Alsatian SME Biosynex is acclaimed. The latter won the first guarantees of quality. “Among the 6 Trods (rapid diagnostic orientation test, Editor’s note) tested, the Abbott, Biosynex and AAZ tests were the most efficient”, notes the evaluation report of the AP-HP and Henri Mondor university hospitals, published at the end of September. Virologist and co-author of the study, Prof. Jean-Michel Pawlotsky specifies that “The 6 antigenic tests evaluated, only on symptomatic individuals, are not sensitive enough to replace PCR in the diagnosis of infection in a symptomatic or contact individual. We could miss 2-3 out of 5 positive people! In contrast, the best antigen tests we have evaluated are very specific. ” In short, the best antigen tests carry a significant risk of “false negatives”.

On the other hand, according to a review of the scientific literature from the Haute Autorité de Santé, the result is very reliable when it is positive. Antigenic tests would therefore be of good quality to distinguish Covid-19 from classic influenza.

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