“There’s a lot of information out there and I know it’s hard for most non-medical, and even medical people, to sift through,” Dr. Jay Marque said Wednesday. “There’s a lot of confusion about which (COVID-19) tests do what.”
Marque, medical director and owner of Lake Charles Urgent Care/Sulphur Family Physicians Urgent Care, spoke to the Sulphur Rotary Club via Zoom regarding the different COVID-19 tests available and some of their drawbacks.
The COVID-19 virus lives in mucus and saliva. At the onset of the pandemic, the most widely available test was a PCR — polymerise chain reaction — test which required that a swab be thrust extremely far up into a nasal cavity. Marque said tests using oral swabbing and swabs from just inside the nostril have now been validated as effective.
He said samples of mucus or saliva are placed in a reagent which “cracks open” the virus’s RNA (ribonucleic acid) molecules to amplify it until it’s detectable. “It’s looking for one spot on the RNA, and, if it detects it, it’s positive,” he explained.
Marque said the tests are so sensitive that they can detect minuscule traces of the virus that aren’t active. One of the unknowns about the virus is the length of time a person is contagious. It’s become a problem for those looking to go back to work at a business that requires two negative PCR tests within 24 hours before returning.
“I’ve personally had people test positive 30 days after their first positive result and they’ve been asymptomatic for two weeks,” he said. “They had one patient at St. Patrick (Hospital) who tested positive 60 days after their first test.” Marque said that is one of the drawbacks with the PCR. “You’re taking a chance on putting somebody out of work when they aren’t contagious,” he said.
Most clinicians believe that within 10 days, if a person has recovered from all their symptoms, they’re okay to go back to work, even if they test positive. The CDC’s current guidance tracks with this belief.
The second test Marque spoke of, the antibody test, was able to get to market faster than the PCR test. These tests use blood to determine if antibodies were created within your body to fight the virus — indicating you’ve had it at some point. Once the IGG antibody develops, that means a person has recovered from the virus. In the context of most other viruses, the IGG provides immunity to a virus.
But another unknown with COVID-19 is how much immunity the antibody provides. “We don’t really know what antibodies mean with this virus yet,” Marque said.
“The FDA got some grief because it took them so long to get the swab tests going, that they kind of took a hands-off approach,” he continued. The FDA put out a statement that anyone who had a test could manufacture it and they weren’t going to stop them, according to Marque. “So there was a flood,” he said. “They have a ton of them coming out of China.” The problem with the lower-sensitivity, finger-prick antibody tests is that there are a lot of false positives.
He said recently released antibody tests that require blood be drawn and analyzed at a lab are nearly 100 percent accurate.
Marque attributes at least some local infections to testing result delays. When staff at his clinics began setting up drive-thru testing in their parking lot on March 14, collected samples were sent all the way to a lab in California, meaning results took about two weeks.
Marque said the clinic would get a positive test result back for someone they had tested two weeks prior and, when the clinic would call them, it was apparent the patient had already gone back to life as usual. “They were semi-recovered and already back out in the community,” Marque said. “You can tell people all day long to quarantine for 14 days, but when they felt better, they were venturing out.”
Test processing has evolved to the point that local labs can provide results within 24 hours. There are some rapid tests that can give results in as little as 15 minutes, but Marque said those aren’t widely available locally. “It’s much better, but we have a long way to to go where it’s truly safe and people can get tested whenever they want,” he said.
Marque said, ideally, there would be unlimited testing and a home test to allow people to test themselves before returning to work.
As of noon Thursday, there have been a total of 291,813 tests performed by state and commercial facilities.