A retail COVID-19 antibody test is now available through M Health Fairview that promotes 99% accuracy and offers an answer to all who believe they have already been infected with the coronavirus that causes the disease.

While leaders of the Minneapolis-based health care system note that the results have limits, they expect broad interest from patients who have wondered for months whether their sniffles and breathing problems were related to COVID-19.

“It helps alleviate a little bit of the worry and the stress that people are experiencing,” said Brittany Hartnett, a Fairview lab client relation specialist. “With just so many unknowns, this test can you give you some sort of an answer.”

Hennepin Healthcare, HealthPartners and North Memorial offer antibody tests, but Fairview is first in the Twin Cities to offer them without the need for a doctor visit or referral.

Rapidly expanding access to the serological blood test comes despite the limited value of the results. A positive test confirms that people’s immune systems produced antibodies in response to infections with the SARS-CoV-2 virus that causes COVID-19, but it doesn’t mean they have “immunity passports” or are free from future risks.

Researchers are examining whether people develop one-and-done immunity, similar to measles, or whether COVID-19 could end up as an evolving and persistent viral threat.

“One of the biggest downsides at the individual patient level is that, if someone tests positive, they consider that to mean that they are ‘immune’ and become more lax in their choices and behaviors with respect to physical distancing, potentially putting ­themselves at risk for re-infection,” said Dr. Elitza Theel, director of Mayo’s Infectious Diseases Serology Laboratory. “Right now, we want to avoid that risk at all costs.”

Mayo’s lab has conducted 180,000 antibody tests, including 70,000 for Minnesota hospitals and clinics.

Minnesota health officials echoed the concern that the state is at a sensitive juncture in the COVID-19 pandemic — with the addition on Wednesday of 578 confirmed cases and eight deaths bringing the state’s totals to 43,742 cases and 1,518 deaths.

A rising case count that landed Minnesota on New York’s travel restriction list this week is one reason for concern, said Dr. Ruth Lynfield, state epidemiologist. “We know that people are sick and tired of precautions and hearing about precautions, but this is not the time for us to let up our guard.”

Deaths and hospitalizations related to COVID-19 have declined over the past month. However, Lynfield predicted more deaths if Minnesota follows the pattern in other states right now of infections among young adults spreading to older, more vulnerable adults.

Plasma donors

One value of antibody testing is identifying patients who recovered from COVID-19 and can donate plasma, which can be used as an experimental therapy for others with severe forms of the disease.

Fairview is offering a $45 test to verify the presence of antibodies and a $55 option to determine whether people would make good plasma donors based on the quantities of antibodies in their blood.

Antibody testing involves blood draws and must be conducted after people have recovered from COVID-19 — usually at least 14 days after initial symptoms. It is different from the diagnostic tests that use nasal or throat swabs to detect active infections.

Insurance sometimes covers antibody tests when doctors request them, but patients must pay out-of-pocket for the retail tests, which are now available by appointment at six M Health Fairview sites.

Antibody testing also can reveal the share of people in a community who have been infected. That can otherwise be difficult to calculate due to the number of infections that don’t produce any symptoms.

The U.S. Centers for Disease Control and Prevention amassed antibody test results from clinics and blood banks last month and estimated 10 unknown infections for every one lab-confirmed case.

A Minnesota sampling of antibody tests from 983 blood donor volunteers showed a lower positivity rate of 1.2%.

While that was surprisingly low, health officials said it could be that blood donors are healthier or not reflective of the general population when it comes to the spread of COVID-19.

Early suspicions

The SARS-CoV-2 virus first emerged in late 2019 in Wuhan, China. Minnesota reported its first known infection on March 6 and its first death on March 21, but some people suspect they might have had cases earlier than that.

Health coach Amber Moberg can’t shake the feeling that her four-week respiratory illness in January — following a vacation in South Dakota — was COVID-19.

Doctors ruled out influenza and strep but “chalked it up as ‘Midwest crud,’ ” the Scott County woman said. She didn’t challenge that because initial antibody tests cost $300.

Mark Haider lost his sense of taste and smell — classic COVID-19 symptoms — shortly before New Year’s Day, leading the Vadnais Heights man to wonder whether he suffered an infection even though it would have occurred weeks before the coronavirus was first identified in the U.S.

“I was sick for four months and lost 25 pounds,” he said.

HealthPartners has found a 4% positivity rate so far based on 2,882 antibody tests, and Hennepin Healthcare has reported an 11% positivity rate based on 740 tests. The need for a referral could explain the higher rates, because doctors would likely have suspicions about patients’ COVID-19 histories before approving testing.

State health officials said they would be concerned if antibody test results undercut their messaging about the need for people to wear masks in public and use basic hygiene practices, such as washing hands and covering coughs.

“There are still questions about immunity and about the length of immunity” after COVID-19, Lynfield said.

Gov. Tim Walz is weighing whether Minnesota should join 20 other states in requiring mask-wearing in public places.

In the absence of a mandate, more retailers such as Walmart are requiring masks in their stores and more evidence is supporting the idea that mask-wearers protect others around them from infection.

The CDC on Tuesday published a case report about two hairdressers in Missouri who wore masks while they had asymptomatic COVID-19 and didn’t infect any of their 139 customers.

Antibody tests could compel people to wear masks and follow guidelines, Hartnett said, if the results quash their suspicions that they were already infected.

“Because it’s a highly accurate test, it would be an answer,” Hartnett said, “whether it’s disappointing or not.”

Fairview is using an Abbott antibody test that received clearance from the U.S. Food and Drug Administration and shows a published accuracy rate of 99%. The secondary test for the quantity of antibodies was developed at the University of Minnesota.