The Food and Drug Administration on Thursday night warned that users of the Abbott ID NOW point-of-care test to diagnose those with the Coronavirus - a test often used by the White House and touted by President Donald Trump - may not be accurate.
"Specifically, the test may return false negative results," the FDA said in a statement.
"We are still evaluating the information about inaccurate results and are in direct communications with Abbott about this important issue," the FDA added.
The Thursday night statement indicated the test was accurate for positive results on the Coronavirus, but that negative results might need to be confirmed with a second review.
President Trump has often talked up the Abbott test as an indicator of how well the U.S. has responded to the virus threat.
"This is a five to 15-minute test," the President said on Monday about the Abbott test. "These tests are highly sophisticated -- very quick, very good. This is things that didn't even exist a short while ago."
"So we do have a great testing capability at the White House," Mr. Trump added.
The FDA statement came a day after researchers at New York University released a study which said the rapid test might miss as many as half of positive cases.
Abbott had questioned the accuracy of that NYU review.
President Trump has alternately trumpeted the growing testing capabilities in the U.S. - and bemoaned them as well.
"We have more cases than anybody in the world. But why? Because we do more testing," the President said during a stop in Pennsylvania on Thursday.
"When you test, you have a case. When you test, you find something is wrong with people. If we didn't do any testing we would have very few cases. They (the press) don't want to write that. It's common sense," Mr. Trump said.