Health officials: Don't use antibody tests for workplace decisions

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Experts question value, accuracy of data, point to low prevalence of virus in county

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Some Ouray County employers have asked workers to get coronavirus antibody tests in order to return to work, against the advice of medical experts who question the tests’ value and accuracy.

In the last seven weeks, 27 people have had blood drawn at Mountain Medical Center for the testing, which measures whether people have antibodies indicating they have been exposed to or recovered from the coronavirus, practice manager Josey Scoville said. According to the Ouray County Public Health Agency, just over one quarter of the 235 of the total tests performed in the county have been serology or antibody tests, rather than the swab tests that detect active virus.

Most of the antibody tests performed at Mountain Medical have been paid for by employers who are mandating that their employees have the tests so they can resume working, Scoville said. Most insurance doesn’t cover it, leaving it to those requiring them to pay.

But using the tests to make those kinds of decisions is in opposition to interim guidelines from the Centers for Disease Control and Prevention, which instructed that “antibody test results should not be used to determine if someone can return to work.” The results also shouldn’t be used to group people together in schools, prisons or other congregate settings, according to the CDC website.

The low prevalence of the virus in Ouray County makes the test results even less useful, Ouray County Public Health Director Tanner Kingery said. “Without a large sample size, it’s just not good data to make decisions on,” he said.

Of the 27 tests done so far at Mountain Medical, 26 people have tested negative, Scoville said. The only person who tested positive for SARS-CoV-2 antibodies was Andrea Iuppenlatz, who identified herself and said she became sick in March and had an antibody test at the clinic in May.

Anyone who wants the test done must make an appointment and have blood drawn at the Ridgway clinic. A courier drives the samples to Grand Junction, where a plane flies them to a Quest Diagnostics lab in Denver for testing. Results usually come within two days, she said. Unlike the nasal swab tests, which detect current infection, the medical center isn’t limited to a finite number of blood tests.

Montrose Memorial Hospital began offering antibody tests to the public this week, but noted that “there is no medical confirmation” that the antibodies offer protection, and the test “does not provide actionable information for your medical provider.” The tests are available for $75 at the Montrose County Event Center, and are available to anyone 18 and older.

It’s not clear what employers are looking for in the results, or whether those who test negative aren’t being allowed to resume work. Scoville said the employers are in Ouray County, but couldn’t provide more information due to patient confidentiality. The Plaindealer was unable to identify an employer requiring the tests to provide perspective on why or how the tests are being used.

“At this point, we don’t understand what to do with that information,” Scoville said. “There is no solid research on what a positive or negative result even tells you moving forward.”

“That certainly has no basis in science,” said Dr. Joe Adragna, Montrose County Public Health medical advisor. “It’s based on hope and assumptions.”

Little is known so far about immunity to the virus, including how long people’s bodies will continue to make the antibodies, and to what extent the antibodies actually provide immunity, he said. While some antibodies provide long-term immunity, others, like those from the common cold, don’t have lasting effects.

Even if people have antibodies, it’s not clear whether they can still transmit the virus from their nasal passages, Adragna said. Based on knowledge from previous viruses, antibodies to COVID-19 will “probably give you some protection and probably be there for some amount of time,” he said, but until further research is done, that’s only speculation.

“It should not be interpreted as proof of immunity, at all,” Kingery said.

There are also concerns about the reliability and accuracy of the test results, due in part to the rapid rollout of different antibody tests over the last few months. “We’ve seen some very, very low quality ones,” Adragna said, which can result in false positives or false negatives.

Others, like the one Montrose Memorial Hospital is currently using to test all of its employees, claim to be 99.1 percent specific, meaning there’s a low chance of finding a false negative. In addition to the quality of the test itself, the community prevalence of the disease also affects how trustworthy the result is.

Tests detecting Immunoglobulin G (IgG) antibodies are more reliable and accurate than those testing for Immunoglobulin M (IgM) antibodies, Adragna said. IgG antibodies typically develop in patients seven to 10 days after symptoms begin, and remain in the blood after the infection, according to National Jewish Health. IgM antibodies may show someone is still infected or has recently recovered, because they’re the first antibodies to begin developing in response to a virus.

Data collected from IgM testing is less useful for both clinical decision-making, when a swab test for active infection would be better, and for research purposes, because the results aren’t as trustworthy, Adragna said.

“There are so many what-ifs,” he said. “Is the test actually representative of a true positive? What level of protection does it give you? What about people who don’t seroconvert?”

Adragna said current research shows 5 to 10 percent of people who recover from the virus won’t experience seroconversion, when antibodies are developed, he said.

“You can’t rest everything on one test, just like policymakers shouldn’t make every decision based on one model,” Adragna said.

The question to ask around antibody testing, he said, is whether it’s going to have an individual benefit or result in a significant change. Currently, people who already recovered from COVID-19 and have antibodies are still being advised to wear masks and practice social distancing, just like people without antibodies, so a positive result shouldn’t change any behaviors.

Antibody testing can be useful, however, for epidemiological purposes and surveillance of the virus’s transmission, rather than for individual decision-making.

So far, about 2.5 percent of Montrose Memorial Hospital employees have tested positive for the antibodies, Adragna said.

Leann Tobin, a spokeswoman for the hospital, said in addition to using the testing for surveillance purposes, “we are also using the testing to show that the precautions we have taken for our staff and patient’s safety has been successful and that staff and providers have access to and are using PPE properly and adequately to protect themselves from infectious patients – and so that infections are not passed from one patient to another.”

Similar widespread antibody testing was done in San Miguel County, paid for by Telluride residents who own a biomedical company. Ninety-eight percent of the 5,455 tests came back negative, with 29 positive results and 79 borderline results, according to the county.

Increased antibody testing could help public health officials learn more about the community prevalence of the virus, which can factor into planning and decision-making.

“We have a lot of models being pushed around from the international, national, state and local level,” all of which include assumptions of a community’s exposure and what percentage of the population is still susceptible, Adragna said. With more antibody test results, those assumptions could be refined, which could in turn impact the models “which can influence policymakers’ decisions as we move forward.”

Liz Teitz is a journalist with Report for America, an organization that places reporters in underserved areas to support community journalism. Want more quality stories like this? Please consider making a tax-deductible donation to the Plaindealer and Report for America here.