Experts Warn Against Using Antibody Tests As It Becomes Available In Hawaii
Antibody tests may be the key to learning how far COVID-19 has spread in Hawaii, and to getting people back to work. However, the state Department of Health doesn’t think the currently available tests are reliable.
Antibody testing is different from the nose and throat swab for the coronavirus, known as a polymerase chain reaction test, or a PCR test.
Dr. James Zehnder, a pathology professor at Stanford University, explained that the two tests serve different purposes.
“The PCR test is telling you whether you have a viral infection at this moment or not. The antibody test is telling you whether you were exposed to the virus and had an immune response,” he said.
“You really need both tests to manage an infection and also to open up the country again, because you need to be able to detect who has an active infection, and know who's had the infection and might have immunity,” he said.
Zehnder explained that a person can take up to two or three weeks after exposure to COVID-19 before testing positive through an antibody test.
He noted it still is not clear if people who have had the virus are protected from reinfection, but it’s likely that the body does build up some immunity.
Doctors of Waikiki, a private practice clinic, started administering COVID-19 antibody tests specifically to first responders. It has purchased about 15,000 antibody tests from Summit Diagnostic Labs and has tested over 200 people.
Dr. Tony Trpkovski, an internal medicine physician with Doctors of Waikiki, said the clinic was looking for a different way to identify people who have been exposed to coronavirus, and heavily researched which antibody test to buy.
“We’re going to help pull out of the community, first responders, people actually working actively with patients in the field because if they’re infected, that’s horrible. They’re going to infect more people,” he said.
“The only tools we have besides social distancing, handwashing, masks is the PCR test and these antibody tests. We have to use what’s at our disposal.”
The test samples the patient’s blood with a finger prick and can process the results in under five minutes.
Tripkovski said Doctors of Waikiki first tested patients they knew had COVID-19 to independently verify that the antibody screening worked.
He said those coming back positive after the antibody test are then also given a standard PCR test to check if they are currently infected. If the PCR test comes back negative, the patient could return to work, possibly with immunity.
However, Dr. Edward Desmond, the health department’s laboratories chief, said the DOH is not advocating the use of antibody tests or immediately getting antibody tests of its own.
“We don't yet know what are the performance characteristics for any of the antibody tests. We're not sure yet about how accurate they are. We don't know whether they're always going to give you a positive result,” he said.
“When the patient has a COVID infection, we don't really know for sure that they're going to give you a negative result when somebody has had an unrelated coronavirus infection. Because of the uncertainty about the performance characteristics of the antibody tests, we're not advocating for that at this time.”
The Food and Drug Administration has allowed antibody tests to be distributed across the country as long as they clearly say they have not yet been approved.
However, Zehnder advised delaying use of antibody tests for now.
“I think it's important to wait, if you can, until there's a reliable antibody test,” he said.”I understand the convenience of having the fingerstick tests, but if you're getting incorrect information, that's really doing a disservice. I think it's important to wait 'til there's reliable testing before you implement it on a large scale.”
The Centers for Disease Control and Prevention is working on reviewing 20 antibody tests for emergency use.
Desmond said the health department is waiting for the evaluations before it would start to administer antibody tests itself. While the DOH is not stopping private medical practices from offering antibody testing, he said he hopes doctors are explaining the test accurately to patients.
“I hope that patients are not being misled to think that they are a diagnostic test, because they're not,” he said.