When Abbott announced they had obtained FDA emergency use approval (EUA) for their BinaxNOW test, a $5 rapid test to diagnose COVID-19, it appeared to be almost too good to be true. The test, which works like a home pregnancy test, can be used with nasal or oral secretions to identify the presence of coronavirus in patients who have symptoms. No equipment is required, although trained personnel are needed. The ability to diagnose infection in less than 15 minutes could allow the use of these devices to screen individuals before they go to work, school, or even to sporting events.
Almost immediately the federal government announced that they would be buying 150 million of the kits to aid in screening of individuals. The exact role that the federal government plans on using this task for was not defined, although the FDA commented, “This test could be used at point-of-care settings, like a doctor’s office, emergency room, or some schools. Given the simple nature of this test, it is likely that these tests could be made broadly available.”
An antigen test detects viral proteins rather than the virus genetic material identified with molecular (PCR) assays. There is also no amplification of the viral material, so these assays tend to be less sensitive than molecular assays. Despite this, they can be run more frequently, and the results are available in minutes rather than days.
“Due to the potential for decreased sensitivity compared to molecular assays, negative results from an antigen test may need to be confirmed with a molecular test prior to making treatment decisions,” the FDA said in its authorization of the BinaxNOW. “Negative results from an antigen test should be considered in the context of clinical observations, patient history and epidemiological information.”
Despite these positive aspects, there are several cautions. The test is only authorized for use in patients suspected of having Covid-19 and “within seven days of symptom onset,” meaning it is not approved to test people who are not clinically ill. This test is identical in its construction to an influenza virus (flu) rapid test that Abbott had to withdraw from the market due to performance issues. As with the Abbott’s ID Now molecular test, where problems occurred in widespread use, this test will need to be evaluated as it is introduced in testing programs.
Hopefully, the BinaxNOW test will usher in a new paradigm in testing for COVID-19.