Antibody test developed for COVID-19 that is sensitive, spec
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An antibody test for the virus that causes COVID-19, developed by researchers at The University of Texas at Austin in collaboration with Houston Methodist and other institutions, is more accurate and can handle a much larger number of donor samples at lower overall cost than standard antibody tests currently in use.

In the near term, the test can be used to accurately identify the best donors for convalescent plasma therapy and measure how well candidate vaccines and other therapies elicit an immune response.

The gold standard of COVID-19 antibody testing measures the amount of virus neutralizing (VN) antibodies circulating in the blood, because this closely correlates with immunity. However, this kind of antibody testing is not widely available because it's technically complex; requires days to set up, run and interpret; and needs to be performed in a biosafety level 3 laboratory.

The research team looked to another type of test, called ELISA assays, that can be implemented and performed with relative ease in a high-throughput fashion and are widely available and extensively used in clinical labs across the world. The ELISA tests, or enzyme-linked immunosorbent assays, look at whether antibodies against specific SARS-CoV-2 proteins are present and produce a quantitative measure of those antibodies.

The goal of the study was to test the hypothesis that levels of antibodies that target two regions of the virus's spike protein--spike ectodomain (ECD) and receptor binding domain (RBD)--are correlated with virus neutralizing antibody levels, making these more accessible, easier-to-perform ELISA tests a surrogate marker to identify plasma donors with antibody levels above the recommended USFDA threshold for convalescent plasma donation.

Researchers used the new test to evaluate 2,814 blood samples used in an ongoing study of convalescent plasma therapy. Houston Methodist became the first academic medical center in the nation to transfuse plasma from recovered individuals into COVID-19 patients.

The researchers found that the ELISA tests had an 80% probability or greater of comparable antibody level to VN levels at or above the FDA-recommended levels for COVID-19 convalescent plasma. These results affirm that all three types of tests could potentially serve as a quantitative target for therapeutic and prophylactic treatments.

Source: https://www.jci.org/articles/view/141206
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