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Certain types of COVID-19 tests less accurately detect virus

Published: Jul. 28, 2020 at 9:53 PM CDT|Updated: Jul. 28, 2020 at 11:13 PM CDT
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FARGO, N.D. (Valley News Live) - One in five North Dakotans have been tested for COVID-19. That’s more than 150,000 tests to date.

If you are going to be tested, experts are finding that the type of test matters.

“Usually it’s a nasal swab or throat swab,” said Dr. Richard Vetter, Chief Medical Officer for Essentia Health West. “Some of the newer ones have saliva where you just get upper respiratory secretions.”

These types of tests have all been used at Essentia in Fargo. They currently use nasopharyngeal, the long swab that enters the nose and to the throat, or nasal tests.

But not all tests are equal.

“The data that I have seen shows that the nasal swabs can be off by as many as 30 percent of the time, about a third of the time,” Dr. Vetter said. “Pharyngeal (throat) swabs were similar. Where the nasopharyngeal might only miss it 10-20 percent of the time.”

Dr. Vetter explains the nasopharyngeal test is the most likely to detect the virus because the further you get away from the respiratory tract, there is more room for error.

“The nasopharyngeal and the nasal swabs are the two most common right now,” Dr. Vetter said.

At Sanford, they say nasopharyngeal is the only test they are using, adding they have has very few false positives or negatives.

But Dr. Vetter also stresses if you are looking for the most accurate result, timing matters too.

“If you do it a few days before you have symptoms or a week or more after symptoms, the test isn’t going to be as reliable or as accurate,” Dr. Vetter said.

Health experts say new technology and studies are surfacing every day as the pandemic continues to impact the nation working to find the most effective way to detect and combat the virus.

Experts also say there has been a lot of questions about antibody testing. This uses blood to see if you have an immune response to COVID-19 and tells you if you had a previous infection but does not tell you if you currently have the virus.

Copyright 2020 KVLY. All rights reserved.

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