Several companies have developed antibody detection tests that are similar to pregnancy predictors. To make these easy-to-use tests, they place virus antigens on strips of paper (nitrocellulose). A virus antigen can be any protein in its envelope. Remember that a virus is something very simple: a capsule that surrounds genetic material in the form of RNA. Since the RNA sequence of the SARS-CoV-2 virus is known, its proteins (antigens) can be produced in the laboratory. These virus proteins adhere to the paper, and a little of your blood is placed on the paper to see if your antibodies butt the virus antigen and if a coloured band appears on the paper, this indicates that you have been in contact with the virus. These are the rapid serological tests. Other serological tests that require the use of machines in laboratories, such as those using the ELISA* technique, are not as fast, but are more reliable.

In a mad rush, several governments bought rapid tests that apparently did not work very well. Spain’s Government bought thousands of these kits from a Chinese company called Bioeasy, and in the first tests it was observed that only 30% of cases were detected. The Chinese company issued a statement saying that the tests were working and that perhaps they had not been used correctly or that there had been insufficient explanation about how to use them. There has been a lot of confusion regarding the reliability of rapid tests. This has been taken advantage of by the rivals of some governments to make jokes saying something like that instead of diagnostic kits they have bought New Year’s Eve party kits. This is not the case either. Initially, rapid tests usually have a lower level of detection than more sophisticated serological tests such as the ELISA. If the ELISA is able to listen to what Materazzi whispered to Zidane, the quick tests on strips of paper only detect a good headbutt that floors.

Therefore, it could be said that a good paper-based antibody test is around 80% effective. When Neymar left F.C. Barcelona, a need arose. They needed someone who was at least 80% of Neymar. That player was Griezmann, but they couldn’t buy him. With nothing equivalent to Neymar on the market, they bought Dembélé, who was 50-60% of Neymar, but with injuries and bad luck he stayed at 30%. Well, something like this has happened to some governments due to the need to buy antibody tests. A serological test with ELISA is Neymar, a good rapid test is Griezmann, and Bioeasy’s Chinese rapid tests are Dembélé.

* ELISA comes from «Enzyme-Linked Immunosorbent Assay.» It is normally done in 96-well plates at the base of which is the antigen recognized by the antibody. The binding of the antigen with the antibody emits a colour that can be quantified with an optical reader. It is a very sensitive technique and allows to quantify the amount of antibody in the sample.

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