SYRACUSE, N.Y. (WSYR-TV) — At-home COVID-19 test kits are not going away anytime soon but are they always reliable?

Some people who have all the signs and symptoms of COVID-19 don’t test positive right away.

So why is that?

“That likelihood of that test being positive if you have COVID, that varies by how long you’ve been infected,” says Global Health Director of SUNY Upstate, Dr. Stephen Thomas.

Dr. Thomas says the longer you’re infected, the more likely it is that you’ll actually test positive. So, the positive result might not come at the first sign of the sniffles.

“If you’re two, three days into your symptoms, those at-home tests should be positive.”

Dr. Stephen Thomas

If it’s not, it could be user error. After all, we’re not all trained in the medical field.

The other factor may be that the virus doesn’t just live in the nose.

“We’ve tested people in the nose and they’ve been negative but then when we go down in the lungs they’re positive,” says Dr. Thomas. “So, it’s also kind of timing.”

If there’s ever any doubt, Dr. Thomas says you should go get a PCR test.