Posted on Aug 03, 2020, 6 p.m.
33 antibody tests have been given the emergency use green light since April 2020 by the FDA, but all of these were designed to provide a yes or no. This serology test is designed to estimate the numbers of antibodies that a person has in their bloodstream from past SARS-CoV-2 infection rather than providing positive or negative results on whether they are present.
It has still not been determined how long COVID-19 antibodies will linger in the body following an infection, and it is still not known how many might be required to provide protective immunity. This type of testing may be able to help identify those that have a strong immune response to this virus.
The latest 2 antibody diagnostic tests getting the emergency use approval are newer versions of previous assays that were developed by Siemens Healthineers to provide a simple yes or no. These tests provide what the FDA describes as a semi-quantitative reading of IgG antibodies and give an estimate of their numbers rather than a precise measurement; these IgG antibodies seem to appear in the blood weeks after symptoms begin to manifest and can be found in the blood much longer after an infection compared to other types of antibodies that were detected in previous tests.
Both of these tests are fully automated tests that are chemiluminescent immunoassays which will tag coronavirus antibodies with reagent markers that produce light through a chemical reaction, the more antibodies present the more light will be produced in that sample.
“Being able to measure a patient’s relative level of antibodies in response to a previous SARS-CoV-2 infection may be useful as we continue to learn more about the virus and what the existence of antibodies may mean,” said Tim Stenzel, director of the FDA’s Office of In Vitro Diagnostics and Radiological Health.
“There are still many unknowns about what the presence of SARS-CoV-2 antibodies may tell us about potential immunity, but today’s authorizations give us additional tools to evaluate those antibodies as we continue to research and study this virus,” Stenzel added. “Patients should not interpret results as telling them they are immune, or have any level of immunity, from the virus.”
The agency also stresses that due to the many remaining unknowns, results from these tests or any other testing should not be interpreted as an indication that a person can stop following distancing procedures or that they should forgo wearing a mask. Additionally these tests are not able to detect whether an infection is active, recovered, or possibly asymptomatic pre-symptom of COVID-19 infection; these tests only detect antibodies the immune system developed in response not the virus itself.
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