How common are false negative, positive tests for COVID-19?

Coronavirus Updates

SALT LAKE CITY, Utah (ABC4 News) – This week, gubernatorial candidate Jon Huntsman, Jr., announced a negative — then a positive — COVID-19 test in the span of two days.

Turns out, his case was unique. Last Thursday, a campaign staffer tested positive for COVID-19, so Huntsman was tested as well. After a few days, the test results came back negative.

But those results were incorrect. How did it happen?

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According to his spokesperson, and his Twitter feed, Huntsman had also been tested about a month ago. The lab incorrectly provided him his first testing results — not his second — which were negative.

The second testing results were thrown out, and Huntsman was tested again — this time, the results came back positive.

“The level of uncertainty and anxiety is very real. And we’re still waiting on some tests for some family members, including one who is more of a high risk category,” said Huntsman on a video posted to social media Wednesday.

There have now been six positive cases of COVID-19 on his campaign team.

His case might be unique, but ABC4 went to the health department Wednesday to ask about “false negative” and “false positive” tests — how common are they?

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First, a response to what likely happened with Huntsman:

“If you have multiple test results in your file that’s in our system, there’s certainly the chance when that human factor comes into play, that somebody could just read the result wrong and return an old result, as opposed to the most recent result, but our understanding is that’s extraordinarily rare and it’s not common at all,” said Tom Hudachko, a spokesperson with the Utah Department of Health.

Hudachko says false negative and positive results are also rare.

A false negative, he says, would be if your test sample were somehow contaminated either during testing or at a lab.

And a false positive, also unlikely, would likely only happen if your body is carrying a virus similar to COVID-19.

Another issue, he says, can be timing.

Health department officials urge folks to get tested seven to 10 days from when they were exposed to someone with a confirmed case.

“If you’re tested too early in the process and you don’t have a lot of virus in your system, there’s a chance the test doesn’t pick up any virus and returns a negative result. Whereas if you get tested at a point where you have a lot of virus in your system, you’re sort of at the height of that wave shape, it’s definitely going to pick up the virus at that point. And it’s going to return a positive result,” said Hudachko.

Nick McGurk
Nick McGurk is an Emmy Award winning journalist and a Utah native — and he couldn’t be happier to be covering news, and raising a family, in his home state.

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