Ohio governor’s COVID-19 results show tests imperfections

WASHINGTON (AP) — Ohio Gov. Mike DeWine's positive-then-negative test results for the coronavirus are a reminder that no test is definitive.

The governor tested positive using a rapid test Thursday, before testing negative later in the day using a more sensitive laboratory-developed test. He was tested because he was going to meet with President Donald Trump during his visit to the state.

No test for coronavirus infection is perfect, and test results can be affected by a variety of factors, including the type of test used, the quality of the sample and when it was taken during the course of any infection.

A look at the types of tests currently used to diagnose COVID-19:

ANTIGEN TEST

DeWine initially received an antigen test, a type of rapid test that uses similar technology for screening for flu, strep throat and other infections on small machines at doctor’s offices.

Instead of detecting the virus itself, such tests look for proteins, or antigens, found on the surface of the virus, which are generally considered a less accurate measure of infection. The test, which uses a nasal swab, takes about 15 minutes.

The tests are relatively new in the U.S. and federal regulators have only allowed two on the market, from manufacturers Quidel and Becton Dickinson. DeWine spokesman Dan Tierney said a Quidel test was used for DeWine; a spokesman for Quidel said the company is looking into the matter.

The biggest risk with antigen tests is that they may deliver false negatives, missing real COVID-19 infections. But they are considered very accurate for ruling out the virus when it is not present, making false positive results highly unlikely.

Some experts have been calling for increased use of antigen tests because they can be developed quickly, avoiding the delayed results...