Validation Study Data Released for Some COVID-19 Antibody Tests

The Food and Drug Administration (FDA) recently released additional test performance data from antibody test kits for coronavirus disease 2019 (COVID-19). The results come from a collaborative effort by the FDA, National Institutes of Health, Centers for Disease Control and Prevention and the Biomedical Advanced Research and Development Authority. 

Each test was evaluated against a panel composed of frozen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody-positive serum samples (n=30) and frozen antibody-negative serum and plasma samples (n=80). The sample size is comparable to that of a typical sample size used to support Emergency Use Authorization (EUA) by the FDA for tests of this type. 

Test performance is based on both sensitivity (ability to identify antibodies to SARS-CoV-2) and specificity (ability to identify no antibodies to SARS-CoV-2); positive and negative values (PPV and NPV) are also calculated to provide understanding of how to interpret the results (ie, how likely it is that a positive or negative result is true). 

One important caveat the FDA noted was that the sensitivity and specificity estimates described in the data may not be indicative of real world performance.

The analysis included results from 2 tests that have received EUA: the SARS-CoV-2 ELISA test (Euroimmun) and the COVID-19 IgG/IgM Rapid Test Cassette (Healgen). 

For the ELISA test, sensitivity to IgG antibodies was 90.0% (27/30) (95% CI, 74.4-96.5); specificity was 100% (80/80), (95% CI, 95.4-100). The PPV at prevalence = 5% was 100% (95% CI, 46.0-100) and the NPV at prevalence = 5% was 99.5.% (95% CI, 98.6-99.8).

The COVID-19 IgG/IgM Rapid Test Cassette showed 100% (30/30) (95% CI, 88.7-100) sensitivity and 100% (80/80) (95% CI, 95.4-100) specificity to IgM antibodies. For IgG antibodies sensitivity was 96.7% (29/30) (95% CI, 83.3-99.4) and specificity was 97.5% (78/80) (95% CI, 91.3-99.3). Combined sensitivity was 100% (30/30) (95% CI, 88.7-100), and combined specificity was 97.5% (78/80) (95% CI, 91.3-99.3). Combined PPV at prevalence = 5% was 67.8% (95% CI, 34.9-88.3), and combined NPV at prevalence = 5% was 100% (95% CI, 99.4-100).

Performance analysis was also included for 3 tests that were voluntarily removed or withdrawn from the notification list. These tests included the COVID-19 IgM-IgG Rapid Test kit (Biomedomics), the COVID19 RAPID TEST (Phamatech), and the SARS-COV-2 IgG/IgM Antibody Detection Kit (Tianjin Beroni Biotechnology). 

“These data are the result of an important cross-government effort,” said FDA Commissioner Stephen M. Hahn, MD. “By posting these data publicly, we’re advancing not only Americans’ access to trustworthy tests, but also the wider field of research into serology testing.”

For more information visit open.fda.gov.

This article originally appeared on MPR