Abbott’s Binax Misses Some Covid Cases, Making Repeat Tests Key

Abbott Laboratories’ BinaxNOW, a 15-minute test for Covid-19, may miss nearly two-thirds of infections in those without symptoms, according to a federal study that suggests repeat testing is needed to catch people when they are most contagious.

The study evaluated results from 3,419 people tested in November with both BinaxNOW and the gold-standard PCR method that detects the genetic makeup of the virus in Pima County, Arizona. The result offers one of the first real-world examinations of how the two approaches stack up against each other.

BinaxNOW, called an antigen test, detected the virus in 64% of those who had symptoms and were positive using the PCR testing approach. But it identified just 36% of those who didn’t have any clear signs of the virus. Both tests accurately ruled out infections in almost all of those who weren’t carrying the virus.

The report was included in the Morbidity and Mortality Weekly Report for the Centers for Disease Control and Prevention. The researchers said the speed and low cost of BinaxNOW, priced at $5 for health care providers and $25 for consumers who have it shipped to their homes, makes it a good way to repeatedly test fixed groups to catch people at their most infectious.

“Despite a lower sensitivity to detect infection, rapid antigen tests can be an important tool for screening because of their quick turnaround time, lower costs and resource needs,” the CDC said in its report.

The 15-minute turnaround time and inexpensive costs can be valuable in limiting transmission when used for serial testing in settings like elementary, middle and high schools, colleges or other places people live in group housing, according to the CDC.

Abbott officials didn’t have an immediate comment.

The study will likely continue to fuel controversy over the usefulness of antigen tests and how they should be used. While they carry advantages, critics have questioned their reliability, particularly among test-seekers who lack symptoms.

Proponents, meanwhile, argue that antigen tests perform better than the gold-standard PCR tests on a key metric — detecting individuals who are likely to transmit the coronavirus to others — when used frequently over a period of time.

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