The differences between COVID-19 PCR tests and rapid antigen tests

Published: January 13, 2022 6:27 PM EST
Updated: January 13, 2022 6:30 PM EST

Two different COVID-19 tests could give you different results.

And both could be right.

That’s the crux of this testing confusion.

It turns out they each have their own role in measuring your COVID-19 status.

“There’s a lot of confusion out there. And it’s also very confusing actually, even for us who’ve been doing this for a couple of years,” said Dr. Kami Kim, Director of Infectious Diseases at the University of South Florida.

Kim is an infectious disease specialist doing her best to demystify COVID testing.

The PCR test is considered the gold standard of COVID-19 testing. It’s extremely accurate in detecting infection, determining with the most certainly whether or not you contracted COVID-19.

“The virus is an RNA virus. So the PCR test is an ultra-sensitive test that can pick out tiny amounts of the virus RNA,” Kim said.

Whereas the antigen test, the common rapid test you might take at home, is less robust in identifying COVID-19. It looks for proteins or for antigens that are given off by an active virus.

As the virus subsides, there is less material to measure.

“As the infection’s resolving the antigen test will turn negative faster, right? So because so that’s where it’s being a little bit less sensitive,” Kim said.

Each form of testing has value.

The PCR is better at confirming the virus which may stay in your system weeks after symptoms subside.

The antigen is less sensitive and looks for shedding virus.

If a negative test is required, the PCR may not provide the best read on contagion.

“It’s great for diagnosis, but it’s not so great for telling you if the virus is infectious,” Kim said.

The speediest option and the key to reentering public life may rely on choosing the rapid result.