Q&A: What PCPs need to know about COVID-19 antibody testing

Since the first antibody tests were authorized by the FDA last month to help identify patients who were infected with SARS-COV-2 and recovered, there have been concerns about access to and performance of these tests.

The AMA issued a letter to Adm. Brett P. Giroir, MD, assistant health secretary of the HHS, expressing the organization’s concerns about these tests and calling for more leadership on testing moving forward to ensure the United States is prepared if the pandemic persists into the fall.

“The current outbreak has taught us what can occur if adequate diagnostic testing is not available in the early stages of a rapidly emerging and serious public health threat,” James L. Madara, MD, CEO and executive vice president of the AMA, said in a press release. “We need continued focus on preparation to ensure widespread access to critical diagnostic testing services is available to meet both current needs and future needs for any potential surge in cases coinciding with the next influenza season. Federal guidance and leadership as we move through new phases of this global pandemic will be critical to the rapid identification and management of new cases as we work together to eliminate this global threat.”

To learn more about the clinical implications of COVID-19 antibody testing, Healio Primary Care spoke with Thomas Ronay, MD, a family doctor from San Francisco. – by Erin Michael

Q: Should primary care physicians encourage their patients to undergo antibody testing?

A: We recommend deciding this on a case-by-case basis. It is critical that the laboratory has a process that has sufficient sensitivity and specificity, and this is not available everywhere. We feel the patients must be informed about how to interpret the test results even before any testing is ordered.

Q: Which patients should be prioritized for testing?

A: There is compelling population health motivation for antibody testing. Populations at high risk for exposure and transmission, and populations at risk for poor outcomes should be prioritized, if availability is limited.

Q: Where is antibody testing offered?

A: This is changing every day for the better. The FDA recommends that this testing be conducted by high-complexity CLIA-certified laboratories. We agree with this limitation, but the downside is that some of the new techniques that will broaden access to testing still lack the accuracy to be reliable.

Q: How reliable are antibody tests?

A: High-complexity CLIA-certified laboratories are already putting out results that are impressive in both sensitivity and specificity. So far, reliability seems to be very good. My dual fear is that a low specificity test shows a false presence of antibodies and that a misinformed patient or medical professional takes the result to mean there is immunity when there is none.

Q: How will the results impact clinical decision-making?

A: This is in flux. We do know that in most cases, a positive result means the patient has been exposed to the virus if they are in a high prevalence region. This is interesting to the patient and to us as a community. We don't know whether the mere presence of antibodies conveys immunity, and we are not sure what it means regarding carrier status.

There are three things that remain on the horizon, but maybe just out of sight. One of them is a rapid antigen test, which would allow us to test for the virus the way we do rapid flu and rapid strep testing. Secondly, we are searching for a test that shows true immunity, and the antibody test does not tell us this now. The third thing we are on the lookout for is a vaccine that could trigger our immune systems to be protected.

References:

AMA. Letter to the assistant secretary for health. https://searchlf.ama-assn.org/undefined/documentDownload?uri=%2Funstructured%2Fbinary%2Fletter%2FLETTERS%2F2020-4-27-Letter-to-Giroir-re-COVID-Testing.pdf. Accessed May 6, 2020.

FDA. qSARS-CoV-2 IgG/IgM Rapid Test – Letter of authorization. https://www.fda.gov/media/136622/download. Accessed May 6, 2020.

Disclosures: Ronay is employed by Circle Medical, a UCSF health affiliate.