PORTLAND, Ore. (KOIN) — If you ordered your four free at-home COVID-19 tests from the federal government on Tuesday, then you might be wondering how to use them.

Dr. Geoff Baird, a pathologist with the University of Washington Medical Center, said rapid antigen tests are a good go-to if you are feeling sick with symptoms of the virus. This can be helpful with heavy demand stretching most testing resources thin.

“The clinical performance of an antigen rapid test is good enough such that you will get a pretty good result, a pretty reliable result,” said Baird, who is the chair of laboratory medicine and pathology at UW’s School of Medicine. “It is a great thing for someone to have either to buy at the drugstore or to have a stash of these things at home, if they have them to access – if they get the sniffles, or a fever, or a cough, or short of breath – to get a really quick idea of what this could be.”

For a PCR test, Baird said, there need to be 100 or 200 viruses on a swab for the test to detect it compared to tens of thousands with a rapid test of an antigen test.

“There’s just a lot more virus that needs to be there,” he added.

Despite rapid antigen tests coming to your doorstep, Baird noted that it’s not good for asymptomatic people to be testing themselves to see if it’s safe to go have a family reunion, to go to a theater or any other event with close quarters because “they really do not have the diagnostic power to suggest that.”