Collection method, sample timing can impact COVID-19 test results
Posted July 13, 2020 5:09 p.m. EDT
Updated July 13, 2020 7:05 p.m. EDT
Raleigh, N.C. — 1.2 million COVID-19 tests have been completed across the state and counting. 87,000 of those tests are confirmed positive.
Are results from a drive-thru "self" tests as reliable as those from a healthcare provider?
5 On Your Side's Monica Laliberte looked into it after hearing different experiences from those who've been tested.
Many drive-thru sites let you swab your own sample. Those who've had it done describe it as "painless and quick."
But you hear a very different experience when a medical professional collects the sample.
"I went to the doctor, and it hurt like the dickens," said Dr. John Sanders, an infectious disease expert at Wake Forest Baptist Health.
5 On Your Side asked if the collection process could impact results.
"The nasal pharyngeal swab tends to be a better test collection site," Sanders said. That's a deep swab a nurse would perform.
"You get more virus from those deeper swabs than from just the nasal swab," he said.
5 On Your Side also asked Dr. George Clarke about the collection process. He's a pathologist with WakeMed in Raleigh.
"If you have someone who's good at coaching you through it, a self-collected specimen could work very well," Clarke said.
While the different collection styles are both approved by the Centers for Disease Control and Prevention, the Food and Drug Administration says the deeper specimen is preferred.
Another thing that can impact results is timing -- when you're tested versus when you were exposed.
"If you go get tested two hours later, it's going to be negative," explained Dr. Clarke. "It takes some time for the virus to infect the cells inside of your airways … and to start to replicate and shed virus. And that's going to take a couple of days."
That incubation period is one reason experts recommend that people wear masks, wash hands and keep distance.
The FDA told 5 On Your Side when samples are collected as intended, studies "have shown relatively comparable performance."