FDA warns that COVID-19 test used by Marin, gives false negatives

The U.S. Food and Drug Administration has issued a warning that a COVID-19 test broadly adopted around the Bay Area — including by Marin County for its new mobile units and by the Tiburon Fire Protection District for routine staff testing — runs a “risk of false results, particularly false negative results.”

In its Jan. 4 warning, the FDA said its emergency-use authorization for Curative’s nasal- and oral-swab tests “is limited to symptomatic individuals within 14 days of COVID-19 symptom onset,” meaning it’s better suited to confirm infection in those already showing symptoms than it is detecting the virus in asymptomatic carriers who can spread the disease to others.

According to a new U.S. Centers for Disease Control and Prevention study published last week, nearly 60 percent of cases are transmitted by those without symptoms, including 24 percent by those who never had them and 35 percent by those who didn’t initially have them.

When the county on Dec. 17 announced its rollout of free testing at rotating sites under a new partnership with Berkeley-based health-technology company Curative, it touted the test as offering higher clinical sensitivity and being more accurate than those previously provided by Burlingame-based Color. Marin joined Alameda, San Francisco, San Mateo, Santa Clara and Sonoma counties in using Curative for its free test sites.

Several days before the county announcement, the Tiburon fire agency — which had previously tested its firefighters, paramedics and support staff monthly using Color’s tests through the county — indicated its own partnership with Curative when it announced it was doubling testing of staff to every other week.

Marin health officials on Jan. 8 issued a statement acknowledging the FDA warning but said it would continue to offer the tests by Curative, which the county said “is working closely with the FDA to address any unresolved concerns and will be providing additional updates and information as it becomes available.”

Curative CEO Fred Turner said in a separate press statement that the company is “confident” in its data.

Marin’s response noted all COVID-19 tests “carry a risk of a false result, and all tests require clinical judgment.”

“Marin County Public Health advises clinicians to treat all patients with a clinical history (exposure or symptoms) consistent with COVID-19 as positive cases, regardless of test result or type of test,” it said.

While the county said “Curative provides 1,000 more tests per day to diagnose cases that might otherwise go undetected,” it did not indicate how many asymptomatic patients have been diagnosed using the firm’s tests or specifically address the FDA’s warning about false-negative results for those who aren’t showing symptoms or are unaware of exposure.

Those tests are common, such as for the routine testing of first responders and health-care, school and other essential workers, or for broad testing after a workplace infection to ascertain and contain potential outbreaks. Residents also frequently use free county systems for required or precautionary tests before essential travel or medical or dental procedures, even though the county separately states it doesn’t provide its tests for such purposes. The Curative tests have not received FDA authorization for any of these types of asymptomatic use. And while the vaccine is being rolled out now to health-care workers and first-responders, a recent survey by the Kaiser Family Foundation found that 29 percent of health-care workers were “vaccine hesitant,” and national reports are showing as many as 20-40 percent of those eligible for the vaccine are declining it.

The FDA warned the risk of false negatives includes “delayed or lack of supportive treatment” and “lack of monitoring of infected individuals and their household or other close contacts for symptoms resulting in increased risk of spread of COVID-19 within the community.”

Further, a decrease in the detection of infected residents at the same time the county is able to ramp up testing with its rotating mobile units could artificially reduce the county’s test-positivity rate, making it appear the community spread of the virus is slowing.

Marin public-information officer Laine Hendricks and county public-health officials did not respond to repeated requests for comment by The Ark’s press time.

Tiburon Fire Chief Rich Pearce said by email Jan. 11 that his agency had been alerted but will continue to use the Curative test.

SFGate.com reports the California Department of Public Health is not using Curative at any of its own test sites. L.A. County says it will replace Curative tests with one by Fulgent Genetics.

Marin’s Curative oral-swab tests are being offered at seven sites, free to those with or without health insurance. The five-day-a-week San Rafael drive-through location, at the Armory parking lot on Armory Drive, operates 8 a.m.-2 p.m. Mondays and Wednesdays, 11 a.m.-5 p.m. Tuesdays, Thursdays and Sundays. The closest of the rotating once-a-week sites are at Sausalito City Hall from 10 a.m. to 4 p.m. Wednesdays and at Piper Park in Larkspur from 10 a.m. to 4 p.m. Thursdays. Appointments must be scheduled in advance through curative.com.

Asymptomatic residents seeking testing who are concerned about the accuracy of the Curative test should contact their health-care providers directly. Testing is also being offered at CVS/pharmacy in downtown Tiburon, Qwest Diagnostics and Dignity Health GoHealth Urgent Care in Strawberry and Medical Center of Marin Urgent Care in Corte Madera.

Kevin Hessel is The Ark’s executive editor. Reach him at 415-435-2652.