FDA publishes validation data from 5 more COVID-19 antibody tests, both authorized and not

by Connor Hale

In early May, the agency delivered its first batch of antibody test performance results, covering a dozen products independently evaluated in collaboration with the National Institutes of Health and the Centers for Disease Control and Prevention. For nearly two months, the FDA had allowed manufacturers of antibody test kits to sell and distribute their products without undergoing agency review, describing the blood tests as less complicated compared to the high-throughput genomic tests widely needed to confirm active cases during the first phase of the pandemic. Companies were required to perform validation testing themselves and could voluntarily submit their results. Now, with many looking for an end to lockdowns and distancing measures, widespread antibody testing may hold the key to understanding a person’s potential immunity to the virus, or at least gauge how far COVID-19 has spread through a community. 

On May 5, the FDA increased its oversight for these blood tests, bringing them in line with the regulatory requirements set for molecular tests. Later that month, the agency listed 28 antibody diagnostics to ultimately be taken off the market. As part of its separate validation efforts with the NIH’s National Cancer Institute and the CDC, a project first announced in late April, a group of oncology researchers and scientists were tasked with double-checking that the blood tests were accurate enough to detect the specific antibodies for the novel coronavirus and not those for other pathogens, which may cause false-positive results.

The five additional tests published this week include two that previously received the FDA’s blessing: Euroimmun’s IgG ELISA test and Healgen’s IgG/IgM rapid testing cassette, officially authorized May 4 and May 29, respectively. Of the remaining three, two were voluntarily withdrawn from the market by their manufacturers—Biomedomics, which developed a rapid fingerstick assay once distributed by BD, and the San Diego-based test maker Phamatech. BioMedomics previously noted that it is working on submitting a newer version of its serology test to the FDA for review. The final test—a single-use, IgG/IgM fingerstick testing strip sponsored by the Tianjin, China-based division of the Beroni Group—was removed from the market after the FDA declined to issue an official Emergency Use Authorization under its new policies. The Beroni Group said it submitted the rapid test for an EUA review on March 26.

“These data are the result of an important cross-government effort,” FDA Commissioner Stephen Hahn said in an agency statement. “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.”

According to the NCI’s validation work, the Beroni test showed a combined sensitivity of 90% and a specificity of 100% for both IgG and IgM antibodies; however, it displayed 30% sensitivity to IgG antibodies alone. When put up against a set benchmark that the novel coronavirus was present within 5% of a population, researchers estimated the test’s ability to accurately provide a positive result at 100% and 99.5% accurate at providing a negative reading. It also showed cross-reactivity, incorrectly highlighting one of 10 HIV-positive samples. Euroimmun’s IgG test demonstrated 90% sensitivity and 100% specificity, with positive and negative predictive values of 100% and 99.5%, respectively, along with no HIV cross-reactivity. Healgen’s antibody test, meanwhile, showed 100% sensitivity and specificity for IgM, and about 97% for IgG. Combined, the test had a positive predictive value of 67.8%, and a negative predictive value of 100%, with no HIV cross-reactivity.

The full dataset of all five tests is available through the agency’s openFDA website.

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