How Spectrum Health works to make sure antibody tests are accurate


GRAND RAPIDS, Mich. (WOOD) — The Centers for Disease Control and Prevention are warning that a test meant to determine whether people were previously infected with COVID-19 could have false positives.

Spectrum Health is providing those antibody, or serology, tests.

“To date, we have tested almost 2,000 patients,” Dr. Adam Caulfield, technical director of microbiology at Spectrum Health, said.

Only 3% of those patients tested positive for antibodies.

“It’s a big enough sample size to indicate we have a very low prevalence of disease in West Michigan,” Caulfield said.

Be that as it may, the CDC said, “Some tests may exhibit cross-reactivity with other coronaviruses, such as those that cause the common cold.”

That the agency said, could result in false positive results.

“Test results do not indicate with certainty the presence or absence of current or previous infection with SARS-CoV-2,” the CDC said.

Lab workers combat both issues by using two tests for confirmation.

“It’s really the coupling of those two tests that give you the best test performance, and that’s the approach we’ve taken at Spectrum Health,” Caulfield said.

Health care workers support CDC guidelines saying the antibody tests should not be used to determine when people should go back to work or how to group them when congregating in places like schools, dormitories or correctional facilities. That’s because positive test doesn’t necessarily mean someone can’t catch the virus again.

“We’ve always supported that,” said Susan Smith, senior director of laboratory at Spectrum Health. “We really, I think, have been very clear that it doesn’t even infer immunity.”

The problem is that research of the virus is still so preliminary.

“There is probably some level of protection after you have a result infection, even if that protection is short-lived, but to date there is not enough scientific data to make claims about overall immunity,” Caulfield explained.

Doctors said getting an antibody test is a personal decision and is valuable if you think you may have had coronavirus. They said it’s not for patients who are still battling the virus.

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