What Makes an Antibody Test Accurate?

With the COVID-19 pandemic continuing to impact society on a global scale, antibody tests have been introduced to aid in the public health response. Antibody tests detect the presence of antibodies to SARS-CoV-2 in the blood. Different from a diagnostic test, an antibody test is intended to show if a person has been previously infected with the virus and developed an immune response. 

Why High- and Low-Affinity Antibodies Matter More than Antibody Class

When a person is infected with a virus for the first time, an immune response is triggered to fight the infection with the production of antibodies. While these early antibodies play an important role in kick-starting the immune response, they have a low affinity for the virus itself, preventing them from binding to the virus and eliminating it. As the immune response to the virus evolves, the immune system produces high-affinity antibodies, which are the antibodies that attach to the virus with the potential to neutralize it. Because high-affinity antibodies develop over a longer period, people who are tested too soon after developing symptoms may not have produced these antibodies yet.

Most of the COVID-19 antibody tests currently in use detect only the antibody class – primarily, IgG antibodies. However, we are learning that in COVID-19, the production of these two antibodies may significantly overlap or even appear when they are not normally expected. This means a person could have both low-affinity IgG antibodies and low-affinity IgM antibodies in their blood, which could skew an antibody test result.

The Elecsys Anti-SARS-CoV-2 test is specifically designed to detect only high-affinity antibodies, regardless of the antibody class. This ability to selectively target high-affinity antibodies increases the overall accuracy of the antibody test.

Knowing the Best Time to Get an Antibody Test

For molecular-based testing, where the purpose is to determine if a person has been infected with SARS-CoV-2, it is crucial testing happens as soon as possible after the onset of symptoms. The purpose of an antibody test, however, is to determine if a person was previously infected with the virus and developed antibodies for it. The optimal time for antibody testing is after the body has had time to develop an immune response. Data so far shows that high affinity antibodies are reliably detectable as soon as two weeks after confirmation of SARS-CoV-2.

While asymptomatic patients may not know when they were exposed to the virus, antibodies can remain in the body for some time. With other coronaviruses like SARS and MERS, high-affinity antibodies typically peak within months of an infection and can last for a year or more.

Elecsys® Anti-Sars-COV-2 Tests Are Here

The Medical Group of South Florida is proud to now offer the Roche Antibody tests. This test provides reliable and high-quality results for clinical decision-making for patients with suspected COVID-19 (coronavirus) infection.  

To ensure we will have a test for you please call 561.622.6111 to schedule your appointment or book through our website here: https://mgsfl.com/book-an-appointment/

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