CT Vacinas, a center formed by researchers at the Federal University of Minas Gerais (UFMG) and the Oswaldo Cruz Foundation (Fiocruz), has developed a test to diagnose COVID-19 with lower chances of a false negative or positive.
The test is of the Elisa type (enzyme-linked immunosorbent assay), a method that has became globally known for the detection of HIV.
In addition to being quick, the test designed by CT Vacinas is cheaper than the other available option, RT-PCR (reverse-transcriptase polymerase chain reaction), which costs from $54.8 to $92 in São Paulo, according to our reporters, who contacted three laboratory chains.
As is the case with other quick tests, Elisa is a serological test (based on the search for antibodies in the blood), except it can only be conducted in laboratory, even though the necessary equipment is relatively simple. After the initial validations, the step is a certificate from Brazil’s national sanitation watchdog Anvisa.
“In the case of Elisa, with a completely different methodology [from that of quick tests], a larger blood sample is collected—one milliliter is required at least. We also need a needle to collect the blood. Detecting antibodies is a considerably more sensitive process,” said CT Vacinas Coordinator Santuza Ribeiro.
“Therefore, even if the patient has small amounts of antibodies, you wouldn’t detect it in a quick test, but you could with Elise. You can’t get an Elisa test from a drugstore, for example. On the other hand, sensitivity is much higher. Another advantage is that Elisa lowers the chances not only of a false negative, but also of a false positive—which is observed when you have a reaction that seems positive, but is actually an antibody against a virus other than Sars-CoV-2, like that of the common cold,” Ribeiro explained.
In the Elisa test developed by CT Vacinas, people with antibodies against other viral diseases, like dengue fever, will not test positive. “The quick test is not capable of differentiating it from other infections,” she added.
In practice, the antigen is fixed onto a polystyrene plate and linked to an antibody with an enzyme marker. If there is a defense reaction against the pathogenic material—in this cases, the novel coronavirus—in the form of antibodies, the material deposited on the plate changes its color.
Due to the structure required to apply the test, the team now seeks support from federal agencies, like the Ministry of Science, Technology, Innovations, and Communications, as well as other public entities and companies, in a bid to escalate production and make the test available to a significant portion of the population.
Ribeiro further mentioned that the Elisa test for COVID-19 was made possible thanks to the enhancement of knowledge shared by the team, which pointed towards the importance of steady investment in science. “At CT Vacinas, we had already developed a rather similar test for other diseases, including non-viral ones, leishmaniasis, Chagas disease, and malaria. The change that was made consisted of placing a molecule capable of detecting the antibody against COVID-19 as a test component.”
“We testes three options and found the antigen N, a component of the viral particle, as the best molecule to detect the antibody against COVID-19,” Ribeiro said. Also according to the coordinator, this is a molecule different from the one used in the development of vaccines.
The proposal for the development of the test was submitted by Fapemig early in March, Ribeiro said, while mentioning the success of the team, which tackled the challenge in three months: “We were so happy. We didn’t know whether we’d have the capacity to make it in such a short time.”