Health Expert Says There’s ‘A Pretty Significant False Negative Rate’ If You Get A Coronavirus Test ‘Too Soon’

PITTSBURGH (KDKA) – Finding out you’ve been exposed to someone with coronavirus can fill you with concern.

“Exposure means being within 6 feet of someone not wearing a mask who has COVID for longer than 15 minutes,” says Dr. Amy Crawford-Faucher of AHN Family Medicine.


But before you rush out and get tested with a nasal swab — which picks up the genetic material of the virus — timing is of the essence.


If you go too soon, the results may not be accurate.


“If you don’t have enough of that virus floating around yet, because it’s too early, then that test cannot detect the virus, and it will come up negative,” says Dr. Crawford-Faucher.


“There’s a pretty significant false negative rate if you test too soon, meaning you may have the disease but the test is negative. So it doesn’t help you and can give you a false sense of security. If you test the second day after an exposure, the false negative rate can be 60 percent. The best we seem to ever get is a little bit, like, 18-20 percent.”


It’s better to wait at least four to five days after exposure, and best to wait even a little longer.


“Seven to eight days is probably optimal,” Dr. Crawford-Faucher recommends.


Going too early could mean coming back for another swab.


“If you have a test that’s negative, and then two days later you get symptoms that are very suspicious for COVID, and you had a known contact, so the risk is high, then I think it’s better to get tested to know for sure,” says Dr. Crawford-Faucher.


Keep in mind, if you’re concerned enough that you have it, you should be isolating yourself for ten days to protect others while you’re waiting to get tested and waiting for the results.


“You’re more than halfway through your isolation time anyway, and if you don’t get your test results back for 3-4 days, it’s a moot point,” she points out.


Dr. Crawford-Faucher says with the recent surge in Pittsburgh, it’s been harder to get tested after an exposure if you don’t have symptoms because of limited supplies.


“It might not be worth the frustration finding a place to get the test and then wait several days to get the results to come back, if what you need to be doing in that situation is isolating yourself,” Dr. Crawford-Faucher says.


Test results do matter from a public health standpoint, for contact tracing and to get a better handle on the extent of infection in the community.