What are the rapid 'antigen' tests coming up on Wednesday?

 What are the rapid 'antigen' tests coming up on Wednesday?

Explicit test - Health Minister Olivier Ferrand announced on Tuesday that the rapid screening tests for the Coronavirus, known as "antigen tests", will be published starting this week. But what are we talking about?

They promise results in just fifteen to twenty minutes instead of two or three days. Health Minister Olivier Ferrand announced on Tuesday that tests to detect the Corona virus, called "antigen tests", will be released urgently this week. But what does it consist of?

First of all, it is important to emphasize that these are not rapid serological tests, which consist in discovering whether a person has been infected with the Coronavirus in the past, but rather “rapid antigen tests,” which have the same purpose as the current standard test, RT-PCR: To find out if you currently have Covid-19. And like the latter, it is made from samples in the gills with a swab.

What are the differences with PCR?

But what is the difference between these two processes? Unlike RT-PCR which consists of searching for the RNA of the virus, that is, the genetic code, the antigen test focuses on the antigen, on the surface of the coronavirus, that is, the place where the antibodies we make to fight the virus.

While one requires heavy laboratory analyzes, as long as it is expensive due to the use of very specific equipment, to detect the genetic material of the Corona virus, the antigen test identifies the virus’s proteins in a few minutes, which in turn identifies the virus. An interesting tool for quickly sorting potentially infected people, at airports or in hospitals for example.

Tape smears ... like a pregnancy test

Based on the same principle as pregnancy tests, by means of a colored stripe, this type of diagnosis can actually be made, in practice, both in the laboratory and in consultation with a general practitioner, or even at a pharmacist.

Is it as effective as a PCR test? Antigen testing is known to be less sensitive than PCR tests that use a technique by which the presence of the viral genome is "amplified" a certain number of times, in order to enable identification of the virus in a sample, even if it is present in trace proportions.

Epidemiologist Michael Mina says on Twitter that running rapid tests that only detect people with a high viral load may still be an interesting thing in breaking the chains of transmission. One real warning remains: a less sensitive test is more likely to fail to detect a patient days or a few hours before the peak of the viral load.