The Problems with Antibody Testing and Why We May Never be Immune to COVID-19
Testing for coronavirus has become widespread in Ohio with pop-up stations and drive-through sampling sites.
Those labs use a nasal swab to test for an active case of COVID-19.
Another type of test is also becoming available.
It uses a blood sample to see if you may have already had the disease.
A Cleveland Clinic researcher says this antibody test is not something we should put much faith in.
Kamran Kadkhoda Ph.D is medical director of the immunopathology lab at the Cleveland Clinic, which handles coronavirus testing for the hospital system.
He said there are two types of test for COVID-19, direct detection and indirect detection.
"Direct detection is what’s done using nasopharyngeal swabs," stuck high up in your nose and then tested for viral genetic material. He says this test is highly accurate.
“The indirect detection," said Kadkhoda, "is when we look at the immune response to the pathogen and look for the proteins the body generates against the virus, typically antibodies.”
And it’s this test that Kadkhoda questions.
“The main problem with antibody testing is the issue with the specificity, meaning generating false positive results. Up to 50% of the cases could be falsely positive,” said Kadkhoda.
The FDA has granted emergency use authorization of more than a dozen antibody tests which are now offered by testing labs across the country.
He says any number of common conditions can fool the test, including having had the flu, or the flu vaccine, arthritis or other autoimmune diseases, or other respiratory viruses.
“But the most important ones are the common endemic coronaviruses, there are four of them, that are the second-most common cause of the common cold,” said Kadkhoda.
That means you can test positive for COVID-19 antibodies even if you’ve simply had a cold.
But Kadkhoda says false positives aren’t his main concern about the antibody test.
What does an antibody test tell us?
“The elephant in the room," said Kadkhoda, "is the lack of clinical usefulness from the antibody test.”
“Even if you have a very highly sensitive and specific antibody test, you still don’t know if that provides protection.”
He says there’s so little known right now about how the immune system mounts a defense against the coronavirus that we can’t be certain that having it once means you’re safe from reinfection.
“So it’s really hard to make a firm conclusion that because you have antibody that necessarily means you’re protected or for how long.”
He says that’s a real concern, because, for example, using antibody data to relax safety protocols or create a registry of ‘immune’ workers could lull us into a false sense of security.
“From every angle you look at this," said Kadkhoda, "it’s not something really useful.”
And Kadkhoda says it goes beyond just the value of testing.
What about long-lasting immunity?
He says our immunity to the novel coronavirus, like resistance to its cousin the common cold virus, may never be permanent.
“We can get infected with those every season, or even more than once during a season,” said Kadkhoda, "and we know generally immunity to coronavirus is short lived, and like the influenza, you have to revaccinate every season.”
All of this leads to the sobering possibility that unlike other successful vaccine programs, a long lasting shield against the novel coronavirus could prove ellusive.
“We may never have the vaccine," said Kadkhoda, "or if we do, there are still questions of whether the vaccine is efficacious enough, if the duration of immunity is more than one year so we don’t have to repeat it every year, or if the virus will become endemic.”
On the positive side, Kadkhoda says the simple measures we have in place, like social distancing, wearing masks, hand-washing, “As long as these are observed, we should be fine.”
Researchers like the Cleveland Clinic’s Kamran Kadkhoda are learning more each day about how coronarvirus attacks our bodies, and how our immune system may or may not be able to adequately fend it off.
But like many experts he said, “we just have to wait to see how it goes…”