These tests will allow us to see the pandemic in four dimensions: the first serological tests begin to come out of the laboratory.

From the alarm that a new disease had been found linked to the Wuhan Live Animal Market until the city was shut down, 24 days passed. In that short space of time, Chinese scientists had to identify the virus, sequence it, design reagents to diagnose it, and take it to clinics in the capital of Hubei. By then, there were already more than 1,000 cases in the city, but we had a fundamental tool: tests.

The famous PCR, the molecular tests that can detect the genetic material of the virus, have been extremely useful for diagnosing acute infection. However, we lack a fundamental leg to understand the pandemic well: serological tests to specifically detect antibodies against SARS-CoV2. Why? Because if we do a PCR test on a person who has already passed the disease, it will be negative. Exactly like someone who has never had it.

Serological tests allow us to see the disease in four dimensions

Louis Reed

PCR ("polymerase chain reaction") is a procedure that allows a fragment of genetic material from a sample to be amplified. A sample is taken from a secretion where the virus (mucus or saliva) should be found and, when the sample is processed, this technique allows us to copy and multiply by millions the RNA chain we are looking for. Just the one that lets us know that the virus is present in the sample.

This makes it much easier to identify disease-causing viruses or bacteria. At the time, it was a revolutionary technique that deserved the 1993 Nobel Prize and, for that reason, it is a well-known and easy-to-use test. Chinese researchers quickly targeted such a test to begin diagnosing. In fact, it is essentially the same test that has been used worldwide.

However, it presents some problems when studying the disease in detail. As I said before, when people overcome the disease definitively and the immune system has eliminated the virus, PCR is negative. A few days ago, we discussed how new positives in cured patients had raised the specter of reinfection in China, Italy, and the rest of the world.

The underlying problem is that we did not have serological tests to identify the antibodies that the patients' immune systems had deployed against the virus. When we said at the beginning of the epidemic that we were not going to have a precise idea of ​​the total number of people infected until we had "seroepidemiological surveys", we thought about precisely this: the only way to know if someone has been infected is by finding those antibodies in their blood. We need evidence to help us draw the epidemic over time, in four dimensions.

Although, obviously, that is not the only utility of this type of tests. Just yesterday, Bill Gates suggested that the fastest way to fight the disease was by using the blood (plasma) of people who have already recovered. With these transfusions, antibodies could be introduced in seriously ill patients and thus 'strengthen' their immune system with "external" antibodies, as is done with other diseases for which we do not have treatment such as Ebola. Serological tests, without going any further, have a very important role in identifying human donors that allow a good generation of this type of therapeutic solutions.

Obviously, there are many teams that are working on the development of this type of test. One of the most promising is this ELISA-based test that has been developed by an international group of researchers. ELISA is an immunoassay technique in which the antibody is localized thanks to an enzyme capable of generating a detectable beacon-like product. In this specific case, the recombinant antigens are linked to a SARS-CoV-2 protein.

As in the case of PCR, it is a very well-known and accessible technique, so a test based on it has a great scope. Therefore, although it is still early to evaluate its real effectiveness in clinics around the world, it seems like excellent news to end a week that has not been full of them.

Image | Trust Tru Katsande

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