Coronavirus: what are "antigenic" tests, now authorized by the government?

With 1.2 million coronavirus tests in one week, France has just broken a screening record.

But faced with the influx of patients, laboratories find themselves clogged and the details of waiting to obtain the results sometimes lengthen up to ten days.

To remedy this, the government now intends to prioritize symptomatic patients, contact cases and health professionals.

But the executive is also relying heavily on new tests, including the "antigenic" test.

Made from samples taken from the nose, it should give results very quickly, between 15 and 30 minutes.

France has ordered 5 million of these tests, which should be delivered by October.  

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A sample in the nostrils for a result in 15 minutes

The antigenic tests are like the PCR carried out from samples in the nostrils, by swab.

But unlike the RT-PCR test, which requires laboratory analysis to detect coronavirus genetic material much faster, the antigen test finds virus proteins much faster, between 15 and 30 minutes.

Indeed, a reagent changes color on contact with the virus.

For healthcare professionals, this time saving should allow the chains of contamination to be broken more quickly.

"The interest is to have the patient immediately next door. We can keep him so that we can immediately tell him that he is positive and what precautions he should take, as well as ask him for contacts. The management of the positive results will be much more efficient, ”explains Samira Fafi Kremer, from the Strasbourg Institute of Virology.

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Tests for the general population, not for people with symptoms or "contact cases"

These tests will be authorized to carry out screening operations in the general population, but not for people with symptoms or "contact cases".

Indeed, the clinical trials of the first versions of these tests were not reliable enough.

The experiments only started this week, hence the call for caution from Olivier Véran.

"In terms of tests, we must first check the robustness of the tools and procedures," the Minister of Health warned Thursday.

In the event of a positive result, the antigen test should thus be confirmed by carrying out a PCR test.

But despite this precautionary principle, and the absence of an opinion from the High Authority for Health, France has already ordered 5 million of these tests.

They should be delivered in October.