Abbott BinaxNOW detects the most infectious Omicron cases, according to the study

Abbott BinaxNOW detects the most infectious Omicron cases, according to the study

The Abbott BinaxNOW, a widely used coronavirus at home test, can detect the vast majority of people infected with the new variant of Omicron and, according to a new real-world study, of more than 700 people using a walk-in test facility in San Francisco visited.

The BinaxNOW is a rapid antigen test that was developed to detect proteins on the outside of the coronavirus. Like all rapid antigen tests, it is less sensitive than PCR tests, which can find even very small traces of the virus. But rapid antigen tests were generally good at detecting people with high viral loads and most likely infectious, although federal health officials have recently sent mixed messages about their usefulness.

The new study, which has not yet been reviewed by experts, found that BinaxNOW detected a total of 65 percent of the infections identified through PCR testing, but 95 percent of the people with the highest viral loads. Among those who had high levels of the virus, the tests caught 98 percent of those with symptoms and 90 percent of those without symptoms, the researchers found.

The test’s performance was roughly on par with what the scientists had observed in previous real-world studies before Omicron showed up, they said.

“It works the way it was designed,” said Joseph DeRisi, a biochemist at the University of California, San Francisco and co-president of the Chan Zuckerberg Biohub and author of the article. “There doesn’t seem to be a performance deficit at Omicron.”

The results come after some preliminary studies questioned whether rapid antigen tests are less sensitive for Omicron than other variants – and whether saliva samples might be a better way to detect the variant than the nasal swabs currently used in antigen testing.

At a Senate hearing on Tuesday on the federal response to the coronavirus, Dr. Janet Woodcock, acting commissioner of the Food and Drug Administration, said scientists are still trying to determine how well the currently approved home tests for the new variant are working.

“We think everyone is discovering Omicron,” she said. “We just find them a little less sensitive than some of the previous variants.”

The new research, which relied on nasal swabs, doesn’t address how early in the course of an infection the antigen tests can detect the variant, as it did in a small previous study, or whether the tests with saliva samples would do better. And the results are not transferable to other antigen tests that have to be evaluated individually, warned the researchers.

However, they suggest that a widely used test – the BinaxNOW – should still be able to detect most infectious Omicron cases.

“This tool is still very important,” said Dr. Diane Havlir, an infectious disease specialist at the University of California at San Francisco and the author of the article.

The new study was conducted on January 3rd and 4th at a free test site in San Francisco. Laboratory assistants each took two nasal swabs from 731 people. The researchers tested one swab from each person with the BinaxNOW test and the other with PCR tests.

Forty-one percent of these people tested positive for the virus in the PCR tests. When they analyzed a subset of these positive samples, they found that 98.5 percent of them were Omicron.

Although the antigen test was missed in a small fraction of people with high virus levels, most of those who tested positive on the PCR test but not the antigen test had low viral loads, said Dr. DeRisi. They may have either been in the earliest stages of infection or recovering from their infections at the time of the test.

Because the tests may not capture those recently infected, the researchers recommend that people exposed to the virus test more than once over a period of a few days.

“People can be on the upswing of the virus and we want to make sure these people are recognized,” said Dr. Havlir.

The study was conducted independently from Abbott, she noted, despite the fact that the company provided BinaxNOW test kits for an earlier study in 2020. The test kits for the new study were provided by the health department, she said.

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Rachel Meadows

Rachel Meadows

Trending topics news writer who enjoys cooking, walking her dog and travel.

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