MUSC tests Blood Connection donors for coronavirus antibodies, explains antibody testing process

As the Medical University of South Carolina opens up COVID-19 antibody testing to all of its employees and first responders in the Charleston, Florence and Lancaster areas, in addition to antibody testing for all The Blood Connection blood donors, many are still wondering what this test is and how confident they can be in the results. 

Satish Nadig, M.D., D.Phil., medical director for the MUSC Center for Cellular Therapy, organized an interdisciplinary group of MUSC researchers that developed an antibody test using plasmid from Mount Sinai Laboratory.

He said MUSC is highly confident in the testing done here because of the two-step process and because of the extensive validation done before it began offering the tests. The antibody tests here show whether people have long-term antibodies to COVID-19, meaning they were exposed to the novel coronavirus and their bodies mounted an immune response. So far, researchers believe it takes about three weeks after someone first becomes ill for these long-term antibodies to show up in the blood. What constitutes “long-term” for COVID-19 is still unknown, however. Long-term antibodies for other viruses can last a few months or decades.

Nonetheless, many are curious about whether they have antibodies. Was that horrible nagging cough and tight chest back in February just a run-of-the-mill virus or was it COVID-19? Because of the scarcity of diagnostic tests early in the pandemic, many people couldn’t get tested.

Now, MUSC is offering antibody testing to all of its employees and to first responders in the regions where it has hospitals.

 

In addition, it’s running antibody tests for anyone who donates blood through The Blood Connection, a blood bank that provides blood to hospitals in North and South Carolina. During the first week that MUSC began offering this service, The Blood Connection sent between 1,000 and 1,400 samples each day, collected from donors across both states. 

Nadig explained how the test works.

The novel coronavirus, or SARS-CoV-2, that causes COVID-19 is one of a family of seven coronaviruses that can infect humans, he said. Three have caused serious outbreaks – SARS coronavirus in 2002, MERS coronavirus beginning in 2012 and now SARS-CoV-2, while the other four cause common colds. This new coronavirus shares 88% of its genetic sequence with SARS coronavirus, Nadig said, which is why it was given the derivative name SARS-CoV-2.

Coronaviruses get their name from their crown-like spikes, and these spikes are a key part of the testing. Using blood serum, the first part of the antibody test looks for a reaction to the receptor binding domain portion of the spike. This is the area that allows the virus to bind itself to human cells. Both SARS coronavirus and SARS-CoV-2 bind to the same area, but MERS coronavirus binds to a different area.

 

A blood sample that tests positive in this first part of the test is considered presumptive positive, Nadig said. That’s because it’s possible the test is actually picking up antibodies to a different coronavirus. Thus, blood samples are subjected to the second part of the test, the confirmatory test, which looks for a reaction to the entire spike protein.

Nadig said the Center for Cellular Therapy validated the test first with commercial proteins and then with three sets of patient samples. The first set of patient samples was collected before COVID-19 jumped to humans, so the team knew those samples would definitely be negative for antibodies. It also validated the test using samples from patients who had tested negative during COVID-19 diagnostic testing and from patients who had tested positive for COVID-19.

The center’s results were then further vetted by the Clinical Chemistry Laboratory at MUSC Health.

People who take an antibody test will get either a positive result, indicating they have antibodies, or a negative result, indicating no antibodies.

However, MUSC cautions that people shouldn’t make decisions about going to work or crowded places based on the results of one positive antibody test. Researchers are still determining what antibodies mean for the strength of immunity to COVID-19 or how long such immunity might last.

The test is useful at the population level, though, to show how much COVID-19 is circulating in the community. It will also help researchers in understanding whether people who have been exposed to COVID-19 are at risk of reinfection. And as tests continue to improve and scientists learn more about SARS-CoV-2, individuals will be better able to make informed decisions about work and community events.

MUSC employees and first responders who want an antibody test should go to musc.care and choose the “COVID-19” button, answer all questions, then select “yes” on the additional information question and enter #covidimmunity in the comments section.

People who are interested in donating blood and getting an antibody test can learn more and make an appointment on The Blood Connection website.