PCR or antigen: Which COVID-19 test is right for you?

What are the differences in COVID-19 testing and what works best for you?


As COVID-19 infection rates continue to spike across the country, so is the need for testing. What are the differences in COVID-19 testing and what works best for you?

You see it inside labs — COVID-19 samples piped from tubes. A common type is called PCR testing, which looks for a virus' genetic code.

"Then we use chemicals and science to multiply that segment of the genetic code and make more and more of it through this chain reaction until we make enough to detect." Dr. Moira Larsen, Executive Director of Pathology at Medstar Health.

Larsen says PCR testing often requires more time and money compared to the antigen test. Where the PCR uses genetic code, the antigen test uses proteins.

"We are using detection of pieces of protein, pieces of virus that are made. Those tests tend to be faster, but they're also much more difficult tests to make and much more difficult to detect," Larsen said.

The difference between the PCR and antigen test is how capable and specific they are in detecting the amount of virus.

"The antigen test is a wonderful test for screening. It's much faster. It's much faster to get out into the community," Larsen said.

Larsen said the antigen test is ideal for testing spread in broad populations. But antigen tests can't detect smaller viral loads, especially when someone is first infected, unlike PCR.

"Certainly, in the hospital environment where we're dealing with extremely sick patients and we need to make sure that we have the most exquisitely sensitive test in order to keep all of our patients safe," Larsen said.

Safer at hospitals, in the office and even on airplanes. The PCR test has accurate and refined results. Larsen says if you get a negative result with the antigen test, follow up with a PCR test and always assume you're positive until both tests prove you're not.

"You have to be very honest with yourself about what you've been doing and what risks you've been taking," Larsen said.