What Is the Difference Between A PCR Test (Nasal Swab) And an Antigen Test For COVID-19?

Reviewed on 2/24/2021

PCR Test (Nasal Swab) vs. Antigen Test For COVID-19

A PCR (polymerase chain reaction) COVID-19 nasal swab test looks for genetic material from the deadly pandemic coronavirus, itself. A positive result means you are infected and should start quarantining. A positive antigen test also means you have an active infection, but this assay looks for protein specific to the virus instead of genetic material.
A PCR (polymerase chain reaction) COVID-19 nasal swab test looks for genetic material from the deadly pandemic coronavirus, itself. A positive result means you are infected and should start quarantining. A positive antigen test also means you have an active infection, but this assay looks for protein specific to the virus instead of genetic material.

Types of diagnostic tests currently used in the U.S. to diagnose COVID-19 virus include PCR tests (nasal swabs) and antigen tests. Both tests can be used to determine whether patients have an active coronavirus infection. 

Differences between the PCR test and antigen tests include: 

  • A PCR test uses a nasal or throat swab or a saliva sample
  • An antigen test uses a nasal swab
  • PCR tests work by directly detecting the viral genetic material (RNA)
  • Antigen tests work by detecting specific proteins on the surface of the virus
  • PCR test results can take from hours to up to one week
  • Antigen test results are available in less than one hour
  • PCR tests have a lower chance of false-negative results (a false negative means the test does not detect COVID even though the patient has it) and are more accurate
  • Antigen tests have a higher rate of false-negatives

The advantage of the PCR test is they are more accurate, but they take a longer time to get results. 

The advantage of the antigen tests is that the results are available quickly, which can allow for more immediate diagnosis and treatment, however, because of the high rate of false-negative, they are less accurate. 

In general, if a person tests positive for COVID-19 with either a PCR test or an antigen test, the diagnosis of COVID-19 is relatively certain. A negative test result is less definite, especially with antigen tests. Patients who have a negative result on an antigen test may need a PCR test to confirm the result.

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Reviewed on 2/24/2021
References
https://www.health.harvard.edu/diseases-and-conditions/if-youve-been-exposed-to-the-coronavirus#:~:text=PCR%20tests%20and%20antigen%20tests,two%20types%20of%20tests