THURSDAY, Oct. 29, 2020 — Which type of COVID-19 test is best?
There are three types of COVID-19 tests. The molecular test, known as the PCR — short for polymerase chain reaction – is considered the most accurate, particularly when taken deep in the nasal cavity.
“The sensitivity of the test is much better when you get that deeper specimen,” said Dr. Catharine Paules, an infectious diseases physician at Penn State Health Milton S. Hershey Medical Center. “Even though it’s uncomfortable, that’s the best way to get the test done.”
Another test is antigen testing, which detects viral proteins in a sample, often obtained from a swab of the lower portion of the nostril or deeper, nasopharyngeal swab.
“These are more likely to be point-of-care tests performed on plastic card-based assays, similar to a pregnancy test where a line will show up if it’s positive for the virus,” said Dr. Melissa George, interim chair of the Department of Pathology at the Milton S. Hershey Medical Center.
“But right now, only a few antigen tests have received FDA emergency use authorization, and they’re only available in small volumes,” George said in a hospital news release.
The third test looks for antibodies after someone has had COVID-19.
If someone is concerned that they might have COVID-19, the best test is the nasal swab with the molecular testing, Paules said. “That will show if you’re actively infected with the virus,” she said in the release.
Point-of-care tests that can be processed in 15 to 30 minutes may be available at some doctors’ offices. But because of its lower sensitivity and higher false-negative rates, it’s better to have tests that are processed in a laboratory.
Antibody test use is limited.
“We’re mostly using them to help us define clinical syndromes that might occur after COVID-19,” Paules said. “For example, multisystem inflammatory syndrome. It’s a serious inflammatory complication of COVID in children. One of the ways that we’ve been able to discover that and diagnose patients with it is through an antibody test.”
As far as whether a positive antibody test should be considered a clean bill of health, Paules advised against that.
“There’s a lot we still need to learn about the virus,” Paules said. “We need to learn if infection protects against reinfection down the road. And if it does, are antibodies the way that we measure that protection? Even if I went and had a positive antibody test today, that would not inspire me to change any of my behaviors. I would still wear a mask. I would still social distance.”
While waiting for test results, it’s essential to continue to isolate.
“If you had some cold-like symptoms — you’re coughing, you have a fever — and you got a test, your next step should be to go home and keep to yourself until that test result comes back negative,” Paules said. “You don’t want to infect anyone else while you’re waiting for those results.”
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Posted: October 2020
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