Serological tests should allow a gradual reopening strategy through the possibility of mass identification of persons immunized against Covid-19. There are already dozens of candidate tests, but their evaluation is delaying their large-scale use.
When and how to start reopening?
The answer now depends on the large-scale use of a new type of serological tests. So far, the diagnostic tests that have been used depend on a genetic amplification technique called PCR (polymerase chain reaction), which makes it possible to detect the virus by analyzing samples taken with a sample from the bottom of the nasal cavity. The Serological test, however, is a blood test that looks for the presence of specific antibodies to the SARS-Cov-2 virus, responsible for Covid-19. These small molecules, glycoproteins, are adapted by the immune system to locate and destroy an identified pathogen. If there are antibodies that match SARS-CoV-2, it means the person has already been infected and is now immune, at least for some time. So you can move freely without the risk of infecting others or yourself.
Dozens of serological tests are currently being evaluated
Dozens of laboratories and companies have already developed or even marketed serological tests that include rapid detection kits and automated methods to test hundreds of samples at once. The potential market is very important, and that is why the race has begun. The question today is what devices are recommended in a strategy of progressive reopening.
As of now, there are already a lot of companies selling their kits to hospitals. In the United States, there are even companies such as MyBioSource and NG Biotech offering coronavirus testing kits online. Some kits can even be used at home: They are in the form of strips in which a drop of blood is placed, just like for diabetics. When the strip changes color, it has the antibodies… But is it safe to base the reopening strategy on self-assessment?
The reliability of the chosen tests must be very high so as not to confuse people because of false positives. Indeed from the very beginning, SARS CoV-2 posed a challenge to the sensitivity of serology. A large part of the population gets infected with different coronaviruses every year. And you have to make sure that the tests detect antibodies against SARS Cov-2 and not the other coronaviruses.
In the United States, the team led by P. Florian Krammer from the Icahn School of Medicine in Mount Sinai has previously published the development of a simple test, providing online instructions on how to carry out the test, so that laboratories wishing to do so can make it. To develop the test, the researchers synthesized the S protein which is located on the surface of the virus and is used as a key to infecting human cells. These laboratory molecules have made it possible to make a test that is only sensitive to SARS-CoV-2. For this purpose, blood samples from three patients with Covid-19 were analyzed and compared with 59 other blood samples taken before the outbreak. Aged between 20 and 70, many of the participants were already infected with the NL63 coronavirus, which causes colds every year and attaches to cells in the same way. No false-positive results have been reported at the end of the study and as a result, the test is now being used in US hospitals.
On the way to a rigorous mapping of the COVID-19 epidemic
The advantage of serology for a gradual deconfinement strategy is that it is technically much easier to perform. Taking Blood samples is much more common than the use of nasal swabs, a technical gesture where the risk of contamination is high. For diagnostic tests, there are also strains in the supply of PCR reagents or even swabs used for sampling. On the contrary, we know how to do serology on a very large scale. Therefore, in addition to the crucial fact of the accuracy of the candidate tests, it is also necessary to assess their potential availability; in other words, the manufacturers’ ability to meet demand for coronavirus testing kits.
However, the massive use of these tests in the coming weeks and months will completely change the situation as it will provide us with an accurate map of this epidemic. The mass testing will tell us what percentage of the population has already been infected with the virus without being aware of it. According to the models, epidemiologists indicate that the number of confirmed cases should be multiplied by 10 to 100.