Antibody testing indicates low rate of antibodies among MUSC health care workers

Early results from antibody testing indicate that just 2% of health care workers have antibodies to SARS-CoV-2, the novel coronavirus that causes COVID-19.

MUSC Health began offering antibody tests to its workforce on April 27. The goal is to expand testing to first responders and other health care workers and, eventually, to the broader South Carolina community.

Pamela Murphy, Ph.D., R.N., system administrator of the Pathology and Laboratory Medicine Integrated Clinical Center of Excellence at MUSC Health, said that 920 tests had been completed in the first week of testing.

“Our lab team implemented this testing so quickly; it’s a real example of the collaboration and dedication to our community at large,” she said.

With a wave of sometimes dubious antibody tests having hit the market in April, the Pathology and Laboratory Medicine ICCE rigorously validated the in-lab Abbott Architect COVID 19 antibody test before releasing it to be used. The test, which requires a blood draw, was made available to the MUSC Health workforce in Charleston and the regional hospitals.

At the same time, an interdisciplinary team from several Medical University of South Carolina departments has been working in parallel with teams at Clemson University and the University of South Carolina to develop a test to ensure that – even if supply chain problems cut off access to those commercially produced, like the Abbott in-lab test – South Carolinians would have access to antibody screening.

“By comparing antibody results over time, we can determine how much COVID-19 is occurring locally and how much mild COVID-19 has occurred among the health care workforce.”

Scott Curry, M.D.

What the results of the tests mean is still being determined.

Nikolina Babic, Ph.D., medical director of the Clinical Chemistry Laboratory at MUSC Health, said the team has high confidence in the positive results it reports. “Given our current antibody positivity rates, approximately 90% of positive results are likely to be true positives,” she said, indicating that a person who receives a positive result does indeed have antibodies to SARS-CoV-2.

But that still leaves some people with false positives – as well as the larger question of whether the antibodies actually confer immunity. Although antibodies generally mean there is immunity, there are some viruses, like HIV, in which antibodies can’t complete their task of killing the virus, and others, like dengue, in which a low level of antibodies might actually make a second infection worse than the first.

Danielle Bowen Scheurer, M.D., chief quality officer for the MUSC Health system, previously cautioned against using a positive result to make work decisions.

“It gives them some reassurance that they probably have been exposed, and they have mounted some protective response, but we don’t want them taking that leap of faith to say, ‘I don’t need protective equipment. I don’t need a face shield or a mask when taking care of a COVID patient,’ or ‘I have free rein from a social distancing perspective,'” she said.

Scott Curry, M.D., associate hospital epidemiologist, said the test is most useful at the population level for scientists modeling the spread of the virus.

“By comparing antibody results over time, we can determine how much COVID-19 is occurring locally and how much mild COVID-19 has occurred among the health care workforce. Some care team members had poor access to PCR testing during March, and others were so mildly ill that they did not pursue testing. Antibody testing helps us understand the prevalence of COVID-19 among our workforce in the weeks before PCR testing was readily available at MUSC Health,” he said.

It’s also important to start testing and getting results now, while keeping in mind that new antibody tests will continue to be developed. These new assays will determine the extent to which those antibodies protect against infection.

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