(WENY)-- At home test kits flew off the shelves during the holiday season. But these tests have a higher margin of error than the PCR test.

Dr. Steven Heneghan, Chief Medical Officer and Vice President of Medical Affairs, says that while both tests are fairly accurate, the PCR test is the better of the two.

"The Antigen looks for the protein on the surface, so its very similar to a home pregnancy test, or a strep test. It looks for those proteins, and if it sees those proteins, it measures positive." He says. 

So why is the PCR test a better test? According to Heneghan, it goes more in depth than the standard at home test kits.

"So a PCR test is a test that looks at the nuclear material of a virus. The test is more complicated, so it replicates and expands the numbers of nuclear material in the test itself. And so it improves the accuracy to that close to 100 percent." He explained. 

The Antigen test "doesn't expand the numbers", and Heneghan explained that this wouldn't trigger a positive result.

When it comes to testing after you believe to have been exposed to the virus, it depends on the type of test.

"So at 5 days, certainly if you had an exposure, and you get infected, within 5 days, the accuracy of both tests should be excellent," Heneghan says, "If you for instance had an exposure, and maybe you're going to visit relatives who may be at risk, and you don't have to wait 5 days, the more accurate test would be the PCR test."

Local health departments are asking individuals who test positive with an at home test kit to self-report to them. Counties in the Southern Tier, like Steuben and Tompkins, have rolled out websites were you can report a positive test.