Due to expanded COVID-19 diagnostic testing availability, the Missouri Department of Health and Senior Services (MDHSS) is encouraging providers to test both symptomatic and asymptomatic individuals, if the clinician’s medical judgment determines it is necessary. At the same time, MDHSS also posted words of caution regarding the use of serological testing, which is not considered diagnostic for COVID-19 but rather detects antibodies which could reveal exposure to SARS-CoV- 2 (the virus which causes COVID-19) or a different infection, including other strains of coronavirus, altogether. The recent MDHSS COVID-19 Serological Testing Quick Facts (Quick Facts) cautions that:

• There are multiple antibody tests for COVID-19 with variable performance.
• At this time, it is not clear which antibody responses are protective or sustained.
• Antibody tests should not be used as the sole test for diagnostic decisions.
• Until more is known about protective immunity, serology results should not be used to make staffing decisions or decisions regarding the need for PPE.
• Overall, serological tests may be better suited for public health surveillance and vaccine development.

The Quick Facts conclude with a link to the Serology/Antibody Test FAQs from the FDA. A close read of those FAQs makes two things apparent. If a provider is using serological/antibody testing for COVID-19 they should proceed with caution in light of the FDA’s relaxed Emergency Use Authorization (EUA) processes for manufacturers that develop and distribute such tests. First, be sure the manufacturer and test is on the FDA’s list of those that have notified the FDA that they have validated their serology test. As widely reported in the news, the manufacturers of many antibody tests on the market have not notified the FDA of validation, so it is important to confirm the exact test brand and its manufacturer are on the FDA’s list for at least some measure of comfort, cold as it may be. Second, be sure the documents containing the instructions for use and test results are accompanied with the following information:

• This test has not been reviewed by the FDA.
• Negative results do not preclude acute SARS-CoV-2 infection. If acute infection is suspected, direct testing for SARS-CoV-2 is necessary.
• Results from antibody testing should not be used to diagnose or exclude acute SARS-CoV-2 infection.
• Positive results may be due to past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E.

Given the increased availability of diagnostic tests in Missouri, ideally providers will be able to focus on those and leave use of serology tests to the State for public health surveillance and vaccine development.