AACC Issues Updated Recommendations on Uses and Limitations of COVID-19 Antibody Tests

Only 64 of the 200 antibody tests on the market have FDA emergency use authorizations (EUAs), and even the authorized tests have varying performance characteristics, making it difficult for labs to select tests and validate them. As researchers learn more about the body's immune response to the virus - and as more people get vaccinated - new questions have arisen about what coronavirus antibody tests should and should not be used for. These tests' performance is also impacted by factors such as the prevalence of the virus in a given population, which complicates result interpretation. And though several professional organizations have issued interim guidelines on coronavirus antibody testing, no guidance to date has thoroughly addressed all of these issues.

To fill this gap, AACC's clinical laboratory experts have developed comprehensive recommendations on how to appropriately implement coronavirus antibody tests. This guidance provides the most current understanding of when these tests should be used, notably emphasizing that antibody tests cannot assess whether patients are responding to the COVID-19 vaccine. Alongside molecular coronavirus tests, antibody tests can aid in the diagnosis of COVID-19, and the guidance particularly recommends this combination of tests to diagnose multisystem inflammatory syndrome in children, a rare but serious complication associated with the disease. Other uses for antibody tests include identifying potential donors of convalescent plasma - a treatment for COVID-19 - and determining the prevalence of the coronavirus in the population, though the guidance cautions that these tests might underestimate the latter.

Another highlight of the guidance is that it provides up-to-date information on the characteristics of antibody tests with EUAs, along with a systematic approach that clinical labs can use to validate the performance of these tests. The guidance also explains how to interpret test results in different common scenarios, and it gives examples of how to clearly report these results so that clinicians get the information they need to provide quality care to COVID-19 patients.

"This document aims to provide a comprehensive reference for laboratory professionals and healthcare workers to appropriately implement SARS-CoV-2 serologic assays in the clinical laboratory and interpret test results during this pandemic," said the guidance's lead authors, Drs. Y. Victoria Zhang and Joesph R. Wiencek. They also noted that, as the pandemic progresses, "clinical laboratory professionals, in collaboration with their clinical colleagues, will continue to play an indispensable role in reviewing the evolving scientific literature and adjusting testing strategies to best serve patient and public health needs during this pandemic."

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American Association for Clinical Chemistry (AACC)