Update on Serological Testing for COVID-19

Over the past few days, the Food and Drug Administration has changed course around antibody testing for COVID-19. Previously, the FDA was requiring companies to notify the agency if they were marketing serology testing. Now the agency is focusing on Emergency Use Authorizations for testing companies.

At this time, only a few companies have FDA approval, and each of these companies use tests that require blood draws for serum testing— not whole blood fingersticks.

MDVIP is actively working with Quest and other companies to acquire these tests and will offer guidance as soon as more information becomes available about the utilization of antibody tests. The commissioner of the FDA has expressed caution for tests that do not have EUA approval and has said that they are now performing their own validation studies for these tests.

Virology experts who have spoken to MDVIP say there is no clear evidence on SARS-CoV-2 antibodies and their relation to immunity at this time. If an antibody test comes back positive researchers don’t yet know when a positive patient stops shedding virulent virus, what level of antibodies is needed to show virologic neutralization, and how long immunity may last.

As with other coronaviruses, it appears that after initial infection, the typical patient will see symptom onset around day five and will begin to develop IgM antibodies around eight days post infection and IgG antibodies around 14 days post infection. Virologic tests can test serum collected from patients at eight days and up to 10 weeks from likely risk of COVID-19 virus exposure or post-onset of symptoms.

If a specimen is collected prior to eight days post-onset of symptoms or likely risk of COVID-19 virus exposure, the patient should be asked to return and provide a second blood sample at least seven days after the initial blood specimen.