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Here's why DeWine got two different COVID-19 test results in 24 hours

WCPO DeWine mask waving.png
Posted at 1:51 PM, Aug 07, 2020
and last updated 2020-08-07 18:51:04-04

“Yesterday was kind of a crazy day,” Ohio Gov. Mike DeWine said Friday, holding up a day-old Columbus Dispatch topped with the front-page news of his own COVID-19 diagnosis.

Much of DeWine’s Friday afternoon briefing on the state’s COVID-19 response was given over to questions about the test that had returned a positive result hours before his scheduled meeting with President Donald Trump — and the two subsequent tests that, hours later, came back negative.

The Ohio State University’s chief scientific officer, Dr. Peter Mohler, teleconferenced to help explain how a single patient could receive two different results in a 24-hour period.

Largely, he said, the distinction comes down to the fact that DeWine received two different types of test: First an antigen test, which Mohler compared to a pair of standard binoculars, and then a PCR (polymerise chain reaction) test, which he compared to a high-powered telescope.

What's the difference? PCR tests analyze samples on a molecular level, allowing scientists to look closely at the RNA and DNA of the virus, if present. PCR tests usually take at least a day to provide a result, although certain patients (including DeWine) may see theirs in hours; most patients, particularly those whose tests are sent to labs processing a high volume of samples, will wait multiple days for theirs.

Antigen tests can provide results within an hour, making them suitable for short-notice results like the kind DeWine needed before his meeting with the president. However, they are also among the least accurate tests currently used by medical professionals, Mohler said.

RELATED: What you need to know about rapid tests vs. PCR tests for COVID-19

DeWine received an antigen test before his scheduled meeting with the president. It came back positive.

He then received a PCR test to double-check the antigen test's results. The lab that processed the second test ran it twice, on two different pieces of equipment, to ensure its accuracy, Mohler said. Both times returned a negative result.

Should you be worried you were given an incorrect result during a previous test? Not likely, according to Mohler. You probably didn't get an antigen test.

More than 90% of the tests administered in Ohio, including at high-volume pop-up testing sites, are PCR tests analyzing samples on a molecular level. Antigen tests are used sparingly and are the only tool that health officials use to confirm cases, according to Tiffany Mattingly of the Cincinnati-based Health Collaborative.

"The National Guard, right now when they're down doing testing at those pop-up sites around the community, those are PCR tests," Mattingly said.

DeWine said his own experience with the antigen test could potentially inform his approach as a state leader when deciding whether (and when) to use such testing in the future.

The state’s current data shows some encouraging signs, he said, particularly in urban areas. New diagnosis totals in Cuyahoga County drop by about 40 each day.

And the Ohio Department of Health on Thursday downgraded Hamilton County’s COVID-19 risk level for the first time since the beginning of the pandemic.

“Hamilton County is really a success story,” DeWine said. “The business community came together, Mayor Cranley, the county commissioners, everybody kind of pulled together, got the message out (that) mask-wearing is just vitally important.”

Hamilton County is now orange on the state’s color-coded risk map, which ranks each county on a four-tier scale from lowest risk (yellow) to highest (purple). It had been red, the second-highest level, for weeks.

“We know the battle’s not over,” DeWine said. “Hamilton County residents, continue to wear the masks. Continue to be smart about the social distancing. Just be careful.”

But as cases decline and mask-wearing increases in urban areas, he said, the opposite happens in rural ones. DeWine said rural counties, including Fairfield, Mercer and Stark, all have lower rates of mask-wearing and higher levels of COVID-19 spread within their communities.