A rapid test made by Quidel could only detect 32 percent of positive COVID-19 cases that were identified by a slower, lab-based test, according to a study conducted by researchers at the University of Arizona, The New York Times reported.
The test, called the Sofia rapid antigen test, could detect the virus in more than 80 percent of people who were symptomatic, but only 32 percent of those without symptoms.
"The data for the symptomatic group is decent," Jennifer Dien Bard, PhD, director of the clinical microbiology and virology laboratory at Children’s Hospital Los Angeles, told the Times. "But to get less than 50 percent in the asymptomatic group? That’s worse than flipping a coin."
The test is only authorized for people with symptoms, but its use in asymptomatic people has been strongly encouraged by the U.S. government, the Times reported. In September, HHS began distributing to states 150 million similar rapid antigen tests made by Abbott.
The Sofia test is much quicker and cheaper than lab-based tests, called PCR tests, but PCR tests are much more accurate. Sofia's instruction manual claims it can detect 96.7 percent of the infections that PCR tests can when used on people in their first five days of illness, the Times reported. But Quidel's test also produced more false positives than PCR tests.
David Harris, a stem cell researcher and one of the study's authors, said some of the asymptomatic people may have been missed because they carried too little of the virus to spread it to others.
Quidel told the Times the test was good for rooting out people who are infectious.
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