Which COVID test should you take? Rapid fact check vs PCR

Are you going to a concert? Do you want to know what causes your cough? Depending on the question, you might need a different type of test.

WASHINGTON – As COVID-19 cases skyrocket to the highest number since the start of the pandemic, it has become increasingly difficult for many Americans to track down a COVID-19 test.

Then when you finally have one, you need to decide what kind of test you need: molecular PCR or rapid antigen? The answer depends on the question you ask the test.

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In what situations should you take a PCR test? What about a rapid antigen test?


  • Dr Amesh Adalja, Principal Investigator at Johns Hopkins University
  • Dr Gigi Gronvall, Principal Investigator and Associate Professor at Johns Hopkins University
  • Dr William Morice, Chairman of the Department of Laboratory Medicine and Pathology of the Mayo Clinic and Chairman of the Laboratories of the Mayo Clinic


If you need to know for sure whether you have COVID-19, a PCR test is the most reliable. If you are asymptomatic and want to check if you are contagious, do a rapid antigen test.


The major difference between the two tests concerns the specificity and sensitivity of the tests. Specific significance If you test positive, what is the likelihood that you actually have the virus? And sensitive sense, if you have the virus, what is the chance that you will test positive?

Antigenic tests, although highly specific, are slightly less sensitive than a molecular PCR test. PCR tests are in fact so sensitive that they can sometimes detect even the smallest amount of virus before or after your period of contagiousness.

“We know that PCR tests can stay positive for weeks after a person has recovered because they are so sensitive,” says Dr. Morice. “They’ll pick up the remains of the infection, which antigen tests probably don’t.”

RELATED: Yes, You Can Test Positive For COVID-19 On PCR Tests For Up To 12 Weeks After Infection

Our experts say the test you take depends entirely on the question you ask it. Do you want to confirm that what you have is COVID-19, or do you check if it’s safe to go to a concert or dinner?

“The antigen test is a great tool because you are asking the test to tell you if you are contagious or not, if you are a danger to others,” says Dr Adalja. He says a PCR should be used by someone who needs to know if what they have is really COVID-19.

“They ask ‘What am I sick of?’ Or “why am I sick? “Says Dr Adalja,” as opposed to just screening to see ‘Am I safe with people? “”

Dr Gronvall points out that timing is going to be very important here. If you’re doing an antigen test to see if it’s safe to go to dinner, a test done that morning won’t give you a reliable answer.

“Testing is a moment in time,” says Dr. Gronvall. “If you are using these rapid antigen tests to reduce the risk of ending up with other people, test as close to the event as possible.”

Both tests are very accurate and will tell you if you have the virus or not. So, in this time when a test can be difficult to locate, using anything you can find to slow the spread will be invaluable.

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