Both Essentia Health and St. Luke’s hospital have an additional form of coronavirus testing in place. But the test is far from a panacea, health experts caution.
Known as serology testing, the blood test looks for antibodies produced by the immune system in response to infections.
Typically, those antibodies show up two weeks after the infection, Dr. Bharat Thyagarajan, pathologist and researcher at the University of Minnesota Medical School, said in a phone interview.
Essentia Health began offering the tests April 24, according to a news release.
St. Luke’s also has the tests, Dr. Andrew Thompson, infectious-disease specialist, said in a statement. But St. Luke’s isn’t using them widely, Thompson said, because of a lack of information about how to interpret the results and fear of obtaining false positive readings.
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Thyagarajan said the rub is that even if the test reveals the patient has had the virus, it doesn’t currently provide assurance that the patient is immune to becoming infected again.
“That’s what everyone is actively researching,” he said.
If serology tests at some point do establish immunity, Thyagarajan said, those receiving positive tests would be able to go on with their lives without worrying about becoming infected or infecting someone else.
But that would be a small subset of people. He estimated only 1%-3% of Minnesota’s population likely has been exposed to the virus. Even in heavily hit New York, the exposed percentage is only 10%-12%, Thyagarajan said.
So Thyagarajan predicted the vast majority of Minnesotans would have negative test results — meaning they would continue having to take precautions until a vaccine becomes available.
The test likely will be offered in conjunction with the PCR nasal swab test that’s used to determine if a patient currently has COVID-19, Thyagarajan said.
When administered widely, the serology test will help researchers better understand the nature of the disease, he said.
“What the research is starting to show us is that most of the people who are infected with COVID-19 do not show a whole lot of symptoms and may not even have shown up to the doctor's office,” Thyagarajan said. “So it helps the epidemiologists and the researchers and even the health care workers get a sense of how truly prevalent the infection is.”
