President Trump has tested negative “on consecutive days” using a rapid antigen coronavirus test not intended for that purpose, the White House physician Dr. Sean Conley said in a statement released Monday before the president began a rally in Florida.
The memo said the president tested negative on a rapid test called Abbott BinaxNOW, but experts cautioned that the test’s accuracy has not yet been investigated enough to be sure that the president is virus-free.
“It doesn’t make much sense in my mind that they should be using the BinaxNOW test for this,” said Dr. Michael Mina, an infectious diseases expert at the Harvard T.H. Chan School of Public Health. “But it’s one additional piece of information.”
The BinaxNOW, which costs $5 and functions like a pregnancy test, looks for a protein produced by the coronavirus. It is most effective when the amount of virus in the body is high, but is much less sensitive than the P.C.R., the gold standard laboratory test. The Trump administration has purchased 150 million BinaxNOW tests and plans to ship them to states for use in schools and nursing homes.
In an announcement of the tests’ deployment to states on Sept. 28, the Department of Health and Human Services cautioned that “results from an antigen test may need to be confirmed with a molecular test prior to making treatment decisions; this may be particularly true for negative results if there is a high clinical suspicion that the patient is infected.”
“Infectiousness should be based more on symptom onset,” said Dr. Ranu Dhillon, a physician at Brigham & Women’s Hospital in Boston. The BinaxNOW, he said, “could be giving false negatives.”
According to guidelines released by the Centers for Disease Control and Prevention, people with severe Covid-19, the disease caused by the coronavirus, may need to isolate for up to 20 days. But it has been unclear when exactly Mr. Trump’s symptoms began, or how severe they have been. On Monday, he departed for his Florida rally without a mask covering his face.
Doctors said it’s somewhat reassuring that Mr. Trump has tested negative more than once, but said without more details from the more sensitive P.C.R. tests, it’s impossible to be sure that he is past the point of infectiousness.
BinaxNOW’s “real power lies in marking someone who is transmissible, not the other way around,” Dr. Mina said. “I think they’re mixing things up a bit.”
In a memo released Saturday night with limited information, Dr. Conley said that Mr. Trump was “no longer considered a transmission risk to others.” That memo did not explicitly categorize the president as “negative” for the coronavirus.