Epidemiologist compares the different COVID-19 tests

(FOX 2) - We've seen both false positives and false negatives when it comes to COVID-19 testing. An epidemiologist explains the differences in the testing methods and what causes confusion.  

Right now the test heath experts really take seriously is called the PCR test, which involves a swab up your nose and then it looks for genetic traces of the virus called RNA. 

"It tests for the RNA of a virus. So when we're looking for COVID-19 cases, we want to see, do you have that RNA in your system? So, people who are actively ill, you would have infectious virus in your body at that point in time for 10 days after symptoms develop. For individuals who are asymptomatic, and even individuals who are symptomatic, you can shed non-viable - so non-infectious virus - for several weeks after you've been sick. So this test can pick up infectious or non-infectious virus," explained Oakland County epidemiologist Kayleigh Blaney.

She said PCR test results might take several days to get back from the lab. 

"If you're getting tested in a hospital, the hospital's going to have that lab on site. They're going to do that PCR right there. If you're getting tested at a doctor's office, they don't have those machines in the office so that test does get sent out," Blaney said. "The antigen tests, those rapid tests that you can get back in about 15 minutes, those are run in-house in the urgent care, in the doctor's office, wherever that test is being run it's being right there."

The antigen test can also be done with the swab of your nose and usually, same-day results are promised. But looking for the antigen of a virus means you're searching for proteins, and even the FDA says a negative antigen test should be confirmed with a PCR test.

"The PCR test, the send-out test, that's the gold standard test. That's ideally the test that everybody would get. In reality, we still have a lot of people getting these rapid tests. So positive results on those shouldn't be discounted. If you're positive you need to stay home, you still need to take those precautions. Isolate from your family. We shouldn't discount those results; it's just not the gold standard we're looking for."

The PCR test isn't perfect either but it's the best we have right now. 

Remember with COVID-19 testing, false negatives seem more common than false positives. 

The other testing is antibody testing, which is a blood test that looks to see if you had the virus at one point.