Since population screening is one of the cornerstones of deconfinement in several countries in Europe, the online marketing of self-tests aimed at detecting Covid-19 is a concern for certain health authorities on the continent.

The latest is Spain, which warned, Monday, May 11, against a screening test sold online 89 euros by the company Covidtest. "It is a health product and it is not allowed to be sold online to individuals," the Spanish health ministry told El País. The Spanish Agency for Medicines and Health Products (AEMPS) also asked on Tuesday that the company should stop marketing its tests "200 of which were sold in five days", according to the daily.

In Belgium, the Federal Agency for Medicines and Health Products issued, on March 18, a royal decree "prohibiting the availability, entry into service and use of rapid tests for the measurement or detection of antibodies related "to Covid-19. This does not prevent companies from defying the ban and offering online tests sold from abroad, such as the company Medakit first based in Brussels, then in Hong Kong, which sells a solution at around 80 €.

An unverifiable reliability rate in the state

Covidtest and Medakit claim that their serological tests have a reliability rate greater than 90% for detecting the presence of antibodies in people who would like to self-diagnose. A figure that emanates from these companies and is unverifiable as is.

The newspaper El País, without predicting the veracity of this figure, indicates however that the Covidtest self-tests are manufactured by a Chinese producer, Safecare Biotech, which had been pinned in 2017 by AEMPS "concerning pregnancy tests (au) false CE marking ".

The company Medakit, contacted by RTBF, spoke of its product as a "first barrier" before the practice of a PCR test - identification of the presence of the virus via a sample in the nose. "Our kits are very reliable," says a manager to our Belgian colleagues. This one also puts forward "the authorization to export" of his company: "(On) a hundred factories which currently produce test kits in China (...), there are only five which are approved by the Chinese government and which have (this) authorization. "

>> Read also: "In France, Covid-19 screening tests are struggling to prevail"

The companies that make self-tests therefore do not all seem reliable, and the United Kingdom had the bitter experience of it last April: according to the New York Times, the British authorities spent $ 20 million for two million kits of home tests that ultimately proved ineffective.

A self-diagnosis which poses several problems

For individuals, "buying a test on the Internet is a danger," says microbiologist Rafael Cantón to El País. "You don't know how it was preserved or what you get."

A serological test, as offered by companies that sell their solutions online, normally detects the presence of antibodies in a person's blood in order to confirm the presence or not of the virus. This is possible in particular by measuring the level of IgM and IgG, immunoglobins which are important for understanding the immune system.

>> Read also: "Covid-19: a faster saliva test in the 'final validation phase'"

Problem: how to interpret the result of a self-test alone at home without medical monitoring? It is against this tendency to self-diagnosis that the Federal Agency for Medicines and Health Products has in particular issued a decree in Belgium. "The use of tests based on the detection of antibodies which have not proven their specificity for detection (of Covid-19) could lead to a misinterpretation of the patient's condition," she wrote.

And the Agency will take several examples where the self-test would not be effective: "The patient can carry the virus despite a negative test result before seroconversion (sufficient level of antibodies in the sample to be detected)", "The lay user could also misinterpret the result due to the lack of scientific knowledge" or "IgM detection tests are likely to give false positive results inducing the measurement in healthy patients."

Finding out whether one is a carrier of the virus far from the conventional detection route also poses a concern for "traceability" of infected persons, as explained to RTBF Carlota Montesinos, head of the serology laboratory at Saint-Pierre hospital in Brussels. "However today, it is important to know the number of positive cases, to advance research."

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