Antibody testing for COVID-19 not as helpful as initially hoped
As southwestern Pennsylvania begins to open back up in the green phase of the state’s COVID-19 restrictions, many had hoped that some form of antibody testing could show who had been infected — even if they did not know they were — and who hadn’t as a way to indicate who was at further risk.
Most hospitals and laboratories in the area have worked to get antibody testing platforms up and running in anticipation of a demand for the testing, and nearly every hospital in the region now has the ability to do the testing.
But in the last few weeks, every level of public health, from the Allegheny County Health Department, to the state Department of Health, to the federal Centers for Disease Control and Prevention, all the way to the World Health
Organization and local hospital officials, have warned against using any antibody test — particularly in a low COVID-19 positive area like southwestern Pennsylvania — to make any public health decisions. The reason?
The high likelihood that with so few confirmed COVID-19 cases — less than 3% of the population in Allegheny County, for example — there is the chance that upward of 50% of antibody testing would provide a false-positive test result.
The false-positive rate in an area like Allegheny County could be high because with so few people having tested positive while they were infected, the likelihood of anyone truly testing positive is already very low. That means the chances of someone falsely testing positive for COVID-19 antibodies because of either problems with the test or problems in identifying other coronaviruses instead — like the coronavirus that causes the common cold — become higher.
“When the disease is rare in the community, as it is in Allegheny County, the number of times you have false-positives may be equal to 50%,” said Dr. Graham Snyder, UPMC’s medical director of infection prevention.
Because of that, the results “may be just a flip of a coin. And that’s for a really good test,” he said.
The state Department of Health does keep track of positive antibody tests, but “whenever we make decisions [about the pandemic] we aren’t counting antibody tests at all,” said Health Secretary Dr. Rachel Levine, who has said that less than 1% of the state’s nearly 77,000 positive cases are from antibody tests.
Allegheny County has a similar view.
“In the Pittsburgh [area], where only about 3% [tested positive], I don’t think antibody testing is particularly helpful right now,” Dr. Debra Bogen, the county’s health director, said. “We will re-evaluate that over time in our community.”
Still, laboratories from national firms like Quest Diagnostics and Lab Corps, to MHS Labs in Monroeville, and UPMC, Allegheny Health Network, Butler Health System, Heritage Valley and St. Clair Hospital all offer the test, although all of the local hospital systems offer it for limited testing and with caution.
Dr. John Sullivan, chief medical officer at St. Clair Hospital, which has done about 100 antibody tests for patients, said in an emailed statement: “We have discouraged physicians from using these tests, as they currently don’t add value in guiding individual patient care, given the cross-reactivity with other strains of coronavirus that are associated with the common cold. They may have value in measuring population exposure. We understand that employers are demanding these tests, and it may represent an opportunity or education.”
Washington Health System, with two hospitals in Washington and Greene counties, and Excela Health, with three hospitals in Westmoreland County, said they are not offering the test at all to patients because of similar concerns.
Stephanie Wagoner, spokeswoman for Washington, said in an emailed statement, in part, that “the World Health Organization cautions that there’s a lack of evidence on whether having antibodies means you’re protected against reinfection with COVID-19. The accuracy of the test, the level of immunity and how long immunity lasts are not yet known. … We do not want community members to test for antibodies and think that they are fully protected. They could still … get reinfected or spread the virus to others as a carrier.”
And that is the basic problem with it, even for those who are using the test for other purposes.
“For people to say now, ‘I was infected. I’m immune. I can go out and be safe,’ Well, those are a lot of leaps we can’t make yet” with the current testing available, said Dr. Thomas Walsh, medical director of AHN’s antimicrobial stewardship program.
Both AHN and UPMC are using antibody testing in a research project with Vitalant, the blood center, to evaluate the many plasma donors who have offered to contribute to the effort to research treatment using the blood plasma of people who were infected and recovered from COVID-19.
“The main purpose [of the antibody test for now] is to do small epidemiological studies” with the antibody tests, said Dr. Kymberly Gyure, chair of AHN’s Pathology Institute. “And to maybe use it as a screen for plasma donors.”
Erin Fronczek, clinical laboratory manager at MHS Labs in Monroeville, understands all of those concerns and the limited use in decision-making the antibody test results should have.
“I do agree with that,” she said. “Until we know more about the antibody response and how useful this is going to be, they should not really be including the numbers in decision-making.”
But she believes that the antibody testing platform that MHS began using May 18 — created by Roche, the Basel, Switzerland-based pharmaceutical and diagnostics company — is as helpful as any of the platforms out there now, and is the same one both AHN and Heritage Valley are using.
“I personally like the Roche assay. It’s specific for high affinity antibodies,” she said. “In my opinion, this one is better than all the others and is getting a lower false positive rate.”
With the right understanding of its limitations, she said, the test results can be helpful.
“There is demand for it,” she said. “I have a lot of calls from directors of nursing homes and physicians. Some corporate clients want to test their employees to get them back to work. Occasionally everyday people will call me. One was a parent of a college student who was sick before this started, and they want to know what the test would show.”
MHS — whose owner, Ravitej Radid, 52, pleaded guilty in federal court in January to taking part in massive Medicare fraud case but whose lab is expected to continue to operate
— performed 240 antibody tests in the first 10 days of its availability with more clients lined up to have the tests done since then.
Dr. Yeshvant Navalgund was one of those clients who asked to have his employees tested recently as he prepared to fully reopen their three pain management clinics in the Pittsburgh area on June 1.
The clinics had seen only urgent pain cases during the pandemic, but with a regular flow of patients expected back, they didn’t want to take the chance of any of them or their employees at DNA Advanced Pain Management bringing COVID-19 into the offices and potentially infecting patients.
They had been watching for months as antibody testing evolved — testing that potentially shows that a person has already been infected with COVID-19 — and heard that MHS Labs was offering the testing on a platform that had been approved for emergency use by the U.S. Food and Drug Administration.
“We looked at various ways to get up and running,” Dr. Navalgund, a co-founder of the clinics, said. “The only solution I could come up with was that the sensible route to go was to hold off for a few weeks to see what the testing provided and then go through testing.”
“We told staff, ‘This is the only way we can open,’” he said.
So in late May, Dr. Navalgund and his clinics’ 16 employees were tested by MHS’s mobile lab, which took blood samples to see if they had COVID-19 antibodies, and a nasal swab to perform a test to see if they were currently ill with the coronavirus.
Dr. Navalgund said he and the other two doctors who work in the clinics were well aware of the federal Centers for Disease Control and Prevention’s caution that any antibody test currently in use in a region with low numbers of confirmed COVID-19 cases could have a false-positive rate of upward of 50%.
“But on the flip side, now we have a baseline for all of our employees at a time when we are about to escalate patient encounters,” he said. “A lot of this is helpful to us.”