Researchers verify effectiveness of new serological tests for COVID-19

Researchers verify effectiveness of new serological tests for COVID-19

Agency FAPESP* – Researchers from the University of São Paulo’s Institute of Biomedical Sciences (ICB-USP) have testified to the effectiveness of three new serological tests for COVID-19. The tests were developed at the ICB itself, and use the ELISA (enzyme-linked immunosorbent assay) method to detect antibodies against SARS-CoV-2 and were effective compared to another test already in use on the market, Elecsys, from the pharmaceutical company Roche.

Published in the magazine Frontiers in cellular microbiology and infectionThe work was supported by FAPESP and was based on 1,119 blood samples from people who had or had not had contact with the disease. The test was conducted at the University of the South Pacific University Hospital throughout 2020, so a scenario without vaccines appears.

In the evaluation, the Elecsys test, marketed by the drug company Roche, had a sensitivity of 96.92% (ability to detect positive cases) and specificity of 98.78% (ability to identify negative cases). The performance of the methods developed at ICB has been approximated. The N-ELISA test, which evaluates a complete coronavirus protein, has a sensitivity of 93.94% and a specificity of 94.40%. The RBD-ELISA test, which uses a portion of the protein escalate of coronavirus, it obtained 90.91% and 88.80% efficiency in these two parameters, respectively, while Delta-S1-ELISA, which uses another part of the escalateshowed a sensitivity of 77.27% and a specificity of 76%.

“We got such good results with the N-ELISA test that we can imagine that it will be used commercially in the future. By adopting a protein that is used commercially, unlike the other two tests, the path is likely to be shorter,” highlights Robert Andrea-Santos, PhD in microbiology and first author of the study.

In addition, RBD-ELISA and N-ELISA tests can be used in the future to distinguish whether the antibody was induced by vaccination or infection. “The efficacy in detecting antibodies against the RBD protein, which is present in all current vaccine formulations, as well as against the N protein, related to exposures to coronavirus, suggests that in future studies there will be potential to distinguish between antibodies produced against the vaccine or against infection when both are used. The two tests,” says Andreata-Santos.

The gold standard for analysis

All tests have been validated against the coronavirus itself by the neutralization test, which is considered the gold standard for this type of analysis. Serum was applied to the test to distinguish neutralized and non-SARS-CoV-2 neutralized samples, and neutral samples were considered positive for COVID-19. These results were then compared with the results of ELISA tests.

The neutralization test, which requires a laboratory with a high level of biosafety because it involves viral treatment, has high sensitivities and specificities, as it is able to calculate a patient’s neutralizing antibody load. “Furthermore, with SARS-CoV-2 neutralization, the probability of an antibody reaction from infection with the coronavirus or one of the other pathogens would be very low,” Andreata-Santos adds.

This method is also able to determine if the antibody is neutralizing (it can prevent further infection) or if it is only a binding antibody (it only recognizes a region of the virus). In this way, the methodology eliminates all doubts that may arise regarding the efficacy data of ELISA tests.

The study was carried out within the scope of the thematic project “Antigenic discovery and development of serological diagnostic methods and vaccine strategies against Zika virus (ZIKV)”, coordinated by Luis Carlos de Sousa Ferreira. Serum collection and sample evaluation by Elecsys, as well as groups of researchers coordinated by Edison Luiz Durigon, Silvia Beatriz Boscardin and Cristiane Rodrigues Guzzo – all from ICB-USP, were collaborating with Paolo Margarido (HU-USP), Ricardo Fouque (HU-USP) and Juliana Banwart. .

The project also received coordination support for the improvement of higher education personnel (Capes) and the National Council for Scientific and Technological Development (CNPq).

Article Validation of COVID-19 serological methods and retrospective examination of health staff and visitors to the University Hospital of São Paulo, Brazil It can be read at:

* With information from the ICB-USP Communications Bureau.

This text was originally published by Agência FAPESP under a Creative Commons CC-BY-NC-ND license. Read the original text here.

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