As the U.S. begins to turn to antibody testing to help navigate new phases of the COVID-19 pandemic, an interagency collaboration will aim to evaluate these diagnostic products and their accuracy.
The FDA will work with the Centers for Disease Control and Prevention as well as the infectious disease and cancer research arms of the National Institutes of Health (NIH) to help generate validation data and make sure blood tests are finely tuned to detect the specific antibodies for the novel coronavirus and not for other pathogens, which may cause false positive results.
“As the country starts to see positive signs that the mitigation efforts, like stay-at-home orders and social distancing, are working in our fight against the COVID-19 pandemic, the question of when we can return to work and resume our normal activities is one of the most critical issues facing our nation,” FDA Commissioner Stephen Hahn said in an agency statement.
“Results from these tests can help identify who has been infected and developed antibodies that may protect from future infection as well as identify those still at risk,” Hahn said, adding that these people could also be eligible to donate convalescent plasma as an investigational transfusion for severe cases.
To date the FDA has granted Emergency Use Authorizations to four antibody diagnostics—also known as serology tests—including three in the past week, with more expected.
The most recent products include an automated, high-throughput test manufactured by Ortho Clinical Diagnostics for its Vitros system; a rapid, point-of-care, fingerstick blood test by ChemBio Diagnostics; and a highly sensitive enzyme-linked immunosorbent assay, or ELISA, developed by New York City’s Mount Sinai Health System. Previously, a point-of-care test from Cellex was given the green light as well.
In March—while more than two dozen molecular tests were being authorized by the agency to identify active infections—the FDA said that it would not object to companies bringing their serology tests directly to market without federal review, under certain requirements.
They would have to be validated prior to use and could not be used as the sole method for diagnosing an infection, according to the agency, which described antibody assays as less complicated compared to the PCR tests aimed at sequencing the virus’ genetic material.
The FDA currently maintains a list of nearly 100 different serology products from manufacturers that have notified the agency of their plans to move forward with commercialization without seeking authorizations. This includes tests marketed by Abbott, BD and several Chinese manufacturers.
The open-door policy for antibody tests has led to some confusion: some test developers have taken the FDA’s listing of unauthorized tests on its website as a sign of the agency’s approval, according to Hahn. “Others have falsely claimed that their tests can diagnose COVID-19,” he said.
“When we become aware of these issues, we have and will continue to take appropriate action against firms making or distributing unvalidated tests or those making false claims, such as issuing Warning Letters requesting that companies stop their unlawful promotion and detaining and refusing fraudulent test kits at the border.”
To clarify the agency’s position, Hahn said the FDA is encouraging developers to request a full Emergency Use Authorization and submit their data in order to provide hospitals and laboratories with the assurance the product has received some level of agency review.
Earlier this month, researchers at Oxford University said that their product evaluations found that most antibody blood tests were not ready to be used in wide-scale screening against COVID-19—with many false negative and false positive results.
Those findings came as the U.K. government considers the use of "immunity passports" to allow people to return to work. However, an incorrect result could send them into harm’s way without enough or without any protective antibodies.
The U.S. government’s validation work will be carried out at the NIH—covering both unauthorized and authorized tests—with assistance from the National Cancer Institute and the National Institute for Allergy and Infectious Diseases. Hahn said the FDA will review the NIH’s results and may use the findings to determine whether the FDA issues an emergency green light to a particular test.
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“The bottom line is that FDA still expects tests to be validated even under our revised policy for tests,” said Hahn. “However, the [emergency use authorization] process or an evaluation by NIH supports greater confidence in test performance.”