PCR and Antigen Tests: What You Should Know
By Kendal Heavner
Last month, Gov. Hutchinson began reporting COVID-19 positivity rates based on two testing methods: PCR and antigen testing. These new terms sparked some amount of confusion.
Most COVID-19 tests can be divided into PCR, known as Polymerase Chain Reaction tests. These tests use different samples to search for signs of COVID-19: PCR tests search for RNA and antigen tests search for active infections within a patient. Both tests are performed in Arkansas, each with their own charms and deficits.
For the medical community, the PCR test is the gold standard for determining if someone has COVID-19. In order for a “confirmed COVID-19 case” to be reported from the Arkansas Department of Health, one must have a positive PCR test result. The antigen tests, while 95% accurate, are not used by the Centers for Disease Control to classify if someone is positive with COVID-19. Therefore, someone testing positive with an antigen test is considered a “probable positive.”
PCR testing is used to identify people who are contagious to others. This test is performed by swabbing the nose, throat, or other respiratory areas to determine if a person has an active infection. Additionally, PCR tests are “so sensitive that they can detect a ‘positive’ weeks after a person is contagious,” according to Jeremy Chrysler, Vice President of Business Development at Inuvo and volunteer with RapidTests.org. This sensitivity can be a problem. For example, if a person who is no longer contagious is found positive with a PCR test, they would be asked to quarantine, an expensive and time-consuming precaution.
Antigen testing has another major benefit. It is fast and less expensive to determine who has an active infection. Results can be ready within one hour after testing – a big advantage over PCR testing, where people can wait days. While still showing a 95% accuracy rate, there may be false negative results. Because of this, a positive antigen test will result in a “probable positive” number from the Arkansas Department of Health. While the small possibility of a false negative can cause concern, the ability of antigen tests to detect an infection quickly and save patients’ time and money is alluring. The Arkansas Department of Health in September began rolling out antigen testing statewide for its county health departments.
Recently, the Fayetteville City Board of Health said daily antigen testing results are needed to make proper health recommendations. Health professionals in the Northwest Arkansas area have requested that all positive tests be reported, regardless of the testing method used. We now see the “probable” and “confirmed” positives within testing result numbers because of this request.
“While PCR is technically a superior diagnostic tool because it is more sensitive, antigen tests could be deployed much more broadly to act as a screening tool to prevent ongoing transmission,” Chrysler says. Arkansascovid.com has updated its data reporting to include the combined confirmed and probable results in its data visualizations.