are serological tests reliable?

Serological tests, which make it possible to detect the antibodies created following an infection by the coronavirus, are still in development. Many of them do not fulfill the specifications for their certification. Their reliability, in particular, poses a problem.

At the end of March, the French government announced that France would acquire serological tests. Since then, things do not seem to have moved much. And due, no Review in the course of conception was approved by the health authorities for the moment.

Olivier Véran, Minister of Solidarity and Health, announced on April 19, 2020 in a televised press conference, that " many tests, manufactured in other countries, circulate and are not validated by French laboratories. Not only are we not sure that they are useful, but we are not sure that they are effective "

In France, NG Biotech, which is developing serological tests in the form of a ready-to-use kit, has obtained financial support from the Directorate-General for Armaments to obtain its approval.

The problem with these tests seems to be reliability and more precisely their sensitivity. " Some of them have 40% false negatives ", announced Olivier Véran in the same press conference. That is, four out of ten tests do not detectantibody while they are present.

Still too low sensitivity

A pre-published scientific study has screened nine immunoassays developed in Denmark. Three are Elisa enzyme immunoassays (Enzyme-Linked Immuno Assay) made by a laboratory technician. The other six are tests called " point of care "(POC), which give rapid results and are achievable outside laboratories, like the NG Biotech kit.

The three Elisa tests have a sensitivity between 67 and 93% and a specificity between 93 to 100%. For their part, the POCs show a sensitivity between 80 and 93% and a specificity between 80 and 100%. But they have only been tested on around thirty people, which is insufficient to approve them. It should be tested on thousands of people with Covid-19 and on as many healthy people.

Crucial Review timing

This study also highlights the fact that the reliability and specificity of the tests improve with the progression of the disease. The results are better for samples taken between 14 and 20 days after the appearance of symptoms only for those made between 7 and 13 days or after 21 days.

The timing of serological testing is therefore important. However, we do not know the immune response induced by the coronavirus. How long does it last? When is it detectable? Many questions remain unanswered on the subject.

These serological kits are important for understanding theepidemic from Covid-19. They would allow the true number of infected to be known since the official count does not take into account asymptomatic or mild cases. They could also play a role in containment exit strategies. At the moment, current immunoassays still require a lot of adjustments to give valid results. As for a vaccine or therapeutic treatment, this could take several months.

This will also interest you

Coronavirus: tomorrow, all masked? SARS-CoV-2. It appeared in China in December 2019. Since then, it has claimed tens of thousands of lives worldwide. To limit the spread of this coronavirus and in the absence of treatment or vaccine, various measures have been devised. Among them, the wearing of a mask.

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