Antibody tests. You’ve likely heard a lot about them by now, but how do they work? Are they accurate? And are they a reliable form of testing for COVID-19?
NBC 7 went behind the scenes inside a testing lab in San Diego to learn more about what happens when you take a test and what to expect.
The NBC 7 crew walked into San Diego-based Genalyte lab building in Sorrento Valley Thursday morning. My photographer and I had to sign a waiver saying we hadn’t expressed any COVID-19 symptoms and pass a temperature screening to get past the lobby doors.
For production purposes, a phlebotomist took my blood sample at the lab. But normally, if one were to take an antibody test with Genalyte, one would have to register online or over the phone and go to the testing site at Del Mar Fairgrounds.
“We’re actually looking for the molecular signature of you having been exposed to the virus in the past,” said Genalyte founder and CEO Cary Gunn. “And that shows up in the form of antibodies and we should be able to detect that three months to a year after you’ve been exposed.”
Once my blood was drawn into two tubes, the sample was turned over the lab tech, who then transferred the blood to a grid roughly the size of two sticks of gum.
The tech then placed that silicone grid with my blood on it onto a tray inside a machine.
“So we have an inkjet printer that puts down bits of the virus on the surface of the chip,” says Gunn. “And when we flow your blood over the chip if you’ve developed antibodies against any of those parts of the virus, your antibodies will bind down to the surface of the chip as if they were trying to attack it. Just like it would in the human body.”
Twenty minutes later, my results were in.
I tested negative for exposure to COVID-19. However, I had antibodies present for other common strains of coronavirus – which are believed to somewhat protective should I be infected with COVID-19.
Gunn says his lab has tested thousands of San Diegans in just the last several months.
“We had an FDA-approved antibody test last year in October,” says Genalyte founder and CEO Cary Gunn. “When COVID hit, we were able to basically dedicate all company resources to converting that previously FDA-approved test to the COVID test.”
About 8% of people Genalyte has tested, tested positive for antibodies to COVID-19. And 70 % haven’t been exposed to COVID-19 but have been exposed to closely-related coronaviruses.
That can be very useful information when it comes to studying the population as a whole, particularly with recent discussions surrounding “herd immunity.”
“About half of more of the people who get this disease don’t have any symptoms at all,” says Dr. Robert Schooley in a Zoom interview. “And so they never would have been tested for viral RNA, and (antibody tests are) a way to find out how many people in our population have already been infected.”
But there are some limitations, says Schooley. For one, antibody tests don’t show up until the second or third week after you had COVID-19.
“So they’re very helpful to determine whether if something that happened in the past was COVID-19,” says Schooley. “But they’re not helpful to determine if you have it right now.”
And if you test positive for antibodies, that doesn’t mean you should throw out your face masks, because antibodies don’t last forever.
“We already know from this disease and other coronavirus infections these antibodies go away quickly,” says Schooley. “And that over several months, when we go back and look for them again, they’re already gone. That’s one of the things that makes us worry about the vaccine. Even antibodies present after receiving a vaccine can go away after a year.”
This is why Schooley says the medical community is still unsure as to whether it’s possible to get COVID-19 more than once.
What about test accuracy?
"Some of the early antibody tests were not put together well, says Schooley. “They weren’t very sensitive and they had false positives. The ones being developed now, particularly the ones that have been to the FDA for evaluation, are pretty good.”
Genalyte’s founder says his antibody test is 99% accurate – significantly more accurate than the cheek or nasal swab COVID-19 tests, which have a 70% accuracy rate due to false negatives. He says that’s because humans don’t always shed the virus in their saliva or nasal cavity.
If you are insured, an antibody test is free, paid for by the CARES Act. If you are uninsured, an antibody test with Genalyte will run you $149.