ST. AUGUSTINE, Fla — If you’re tested for the coronavirus, you hope the test result is accurate. We’re learning there are some gray areas when it comes to testing.
Christina Smith of St. Augustine was hospitalized with COVID-19 in March.
She was tested for the virus with the nasopharyngeal method. It’s the long swab that goes up the nose and to the throat. The results came back and “it was 50/50,” Smith said.
Fifty-fifty. How can that be?
“The test has some limitations on it for what it can do,” Dr. David Caro said.
He is the Disaster Medical Officer at UF Health Jacksonville. Caro said he’s heard of several instances in which the results for one person vary. A person could test “positive, then negative, and then positive again.”
Caro said results depend on how the test was performed. He said timing also makes a difference.
“Some of it is what stage in the infection you’re at,” he said. “There are times when you’re infected where certain tests will be positive and certain others will be negative.”
Smith’s 50/50 case led to some second-guessing inside the hospital.
Her husband Roger, said, “When the senior nurse was at the door, another nurse walked up and said, ‘what do we have?’ And she said, ‘(Smith) is 50/50. And you know what that means. That means she’s 50% positive.’ And the other nurse said, ‘why isn’t she on the COVID floor?’ And the senior nurse said, ‘because she’s 50% negative.’”
"I think every hospital in the area is dealing with that kind of issue and the confusion that surrounds that when we get these ‘unsure’ results,” Caro said.
He says a false-negative rate for that kind of swab testing is less than 5%, according to the manufacturer. That’s also under ideal conditions.
The CDC is working on to improve COVID-19 testing.
As for Smith, a blood test result later showed she was positive for COVID-19.