UPDATE-Although Ohio Governor Mike DeWine initially tested positive for COVID-19, when he was screened at the airport before greeting President Trump yesterday in Cleveland; after re-testing, twice, his test results came up negative.
That's because the first one administered, was a rapid result "antigen" test, which has been widely reported to be less accurate than the second kind of test he took, known as a "PCR" test. It is the kind of test that is most often given to people, but which takes longer to process.
DeWine says "We will be working with the manufacturer to have a better understanding of how the discrepancy between these two tests could have occurred."