KNOXVILLE, Tenn. (WATE) — George and Lottie Richardson took several precautions to avoid COVID-19 ahead of their long-planned Caribbean cruise. The cruise line they chose requires two things: proof of vaccination and a negative test within days of leaving.

They followed Carnival Cruise’s procedure but when the test results were read they had tested positive for the virus. The positive tests would have left their daughter Jourdan and other family members to go without them.

“This was a rapid COVID-19 test that is administered through the nose,” Lottie said. “And you can wait while you’re there in the office to get the results of it; that’s the rapid part.”

George said neither he nor Lottie showed any symptoms for the virus and both had been fully vaccinated. They had their vaccination cards as proof.

“You’re both positive, you and your wife,” George said. “I didn’t say anything to them, but I’m thinkin’ to myself, this can’t be.”

“That was devastating because we felt that was not possible for us,” Lottie said. “We don’t go to work; we’re at home. We’ve been closed in since it all began. It’s just been George and I.”

As they started looking they found a drive-thru free COVID-19 testing site on Cumberland Avenue offering the nose swab PCR test. No appointment was needed and the results would take about 15 minutes.

“They found the results and they were negative, which I wasn’t surprised,” George said.

The family got to enjoy their cruise together and no one was sick. However, they wondered why they were found positive and negative on the same day just hours apart.

We asked Dr. Eric Penniman, medical director of Summit Medical Group. Summit Medical did not test George or Lottie.

“So in this case the couple had two false positives, each of them having a false positive,” Penniman said. “So we know the specificity of even the rapid COVID test is really good, it’s like ninety-seven percent. Meaning the likelihood of a false positive is only about three percent. So each of them ended up with a false positive which is a pretty unusual scenario.”

Penniman said the Richardsons did the right thing in seeking another test.

“It is perfectly fine that they went and had the rapid test, but it is pretty unusual that they both got false positive results.”

Penniman said interpreting the results of a COVID-19 test depends on two things: the accuracy of the test and the pretest probability, or the estimated risk of disease before testing.

The risk of disease for the Richardsons was low because they were fully vaccinated, avoided crowds, wore masks when they were in public places, and had no symptoms of the virus.