In-Depth: Should San Diego school districts rely on rapid testing during the omicron surge?

Rapid antigen testing COVID
Posted at 8:22 PM, Jan 11, 2022
and last updated 2022-01-11 23:57:09-05

SAN DIEGO (KGTV) – Students in Chula Vista, Cajon Valley, and National City returned to campuses Tuesday from winter break, one day after their school districts distributed rapid at-home COVID test kits to families.

The tests, which deliver results in about 15 minutes, are designed to give parents an added layer of assurance. But emerging research shows rapid antigen tests are less sensitive to the omicron variant, particularly in the early stage of infection.

A small study by the Covid-19 Sports and Society Working Group found that people harbored infectious levels of omicron for about three days before rapid tests by Abbott or Quidel detected they were positive.

On Monday, UC San Francisco released a larger analysis of Abbott’s BinaxNOW rapid antigen test. The study compared results on more than 700 swabs to a laboratory-based PCR test. It has not yet been peer-reviewed.

Among those with symptoms, the rapid antigen test was 87 percent accurate at identifying infections. However, it was just 65 percent accurate overall during the wave of omicron cases.

Last year, the same researchers found Abbott’s rapid test was 89 percent accurate overall against earlier variants.

The authors stressed that two rapid tests, taken days apart, are needed to reliably assess people without symptoms during the omicron surge.

San Diego Unified’s consulting physician, Dr. Howard Taras, acknowledged that rapid tests are likely failing to detect a significant number of infected students.

“Many kids are probably positive in school with omicron,” he said.

Still, public health experts believe that rapid tests remain helpful to identify people who are the most infectious. And they stress that schools remain safe despite the imperfections of the tests.

“I’m not as bothered as I used to be knowing that there are asymptomatic positive kids in our school system if I know that there’s very, very tight adherence to how well your mask is on and that they’re eating outdoors,” Taras said.

Across California, the state says it has now distributed more than 7.6 million rapid tests since Governor Gavin Newsom promised one for every schoolkid in December.

Weather delays hampered the effort, but the state has now delivered enough test kits for all 500,000 K-12 public school students in San Diego County, said San Diego County Office of Education spokeswoman Music Watson.

Governor Newsom has proposed spending $1.2 billion to bolster testing efforts, including the high-profile push to send at-home kits to every student in the state. The California Department of Public Health did not immediately respond to an inquiry about the exact cost of the rapid testing program at schools.

Was it money well spent? Dr. Omid Bakhtar, laboratory medical director at Sharp Healthcare and a member of the county’s testing task force, says absolutely.

“When you use a [rapid] test in the appropriate setting, with the appropriate expectations, it’s a very useful test. It all breaks down when the expectations are wrong,” he said.

Dr. Bakhtar said parents should treat a single negative rapid test with suspicion, particularly if they suspect their child was exposed. Ideally, parents should perform a second rapid test three days after the first.

But the UC San Francisco study found a positive rapid test remains more than 99 percent reliable against omicron.

Across the state, rapid at-home tests have had an impact. Sacramento City Unified was able to detect more than 500 infections following the winter break. Oakland Unified detected more than 900.

San Diego Unified was among the local districts that received test kits well before classes resumed. It was able to find and isolate at least 1,700 students before classes resumed for the winter break, Dr. Taras said.

“Removing those children from being around other children for a period of time is unquestionably beneficial and is money well spent,” Dr. Bakhtar said.