Avance Care, a primary care provider based in the Triangle, introduced rapid, same-day COVID-19 testing this week, Chief Medical Officer Joanne Fruth said.
Avance Care already provides COVID-19 testing for both active infections and antibodies at its South Chapel Hill facility in Chatham County. But this newly introduced test — called the rapid antigen test — is different from the “PCR” test Avance Care has been administering since the end of March, Fruth said.
A PCR (or polymerase chain reaction) test detects the virus’ genetic material, or RNA.
“(It’s) done in the lab,” Fruth said.
Nurses swab the back of a patient’s throat or nose for cells, and then they send the swab off to a lab, where lab technicians isolate the genetic material and trigger a reaction that replicates the tiny viral molecules. This step increases the sample size lab technicians can analyze, providing a more accurate result.
The test usually takes a few hours, and many North Carolina patients who undergo this type of testing receive their results back within three to four days — and sometimes longer if labs are backlogged.
The rapid antigen test, Fruth said, detects antigens, or proteins that shoot off of viruses and cause immune responses within their hosts.
“(The antigen) meets up with a chemical in a reaction and then that’s scanned,” she said. “It’s called immunofluorescent detection.”
It takes about 15 minutes to perform and turns around results that same day. It can be done in the office, too. But it’s not perfect, Fruth warned.
“While it sounds attractive,” she said, “it does come with some limitations that we want people to be aware of.”
The test, which the FDA granted emergency use authorization earlier this year, is only as good as the virus particles it can detect. For individuals with few viral antigens in their noses or throats — like people without symptoms or in the early stages of infection — the test may not be able to detect enough viral particles to provide an accurate result.
“For that reason, we can’t use our rapid antigen test to screen asymptomatic individuals,” Fruth said, adding: “It’s not going to be that test that’s going to clear you for your surgical procedure or to clear you for entrance into school.”
It’ll be most accurate in patients who demonstrate symptoms, such as a cough, runny nose or fever, she said, a group the Center for Disease Control estimated on July 10 to account for about 60% of people infected with the virus.
When someone has symptoms consistent with COVID-19, Fruth said “a positive (antigen) test has good validity.”
Yet Avance Care providers may recommend that symptomatic people also get a regular PCR test alongside the less sensitive rapid antigen test.
“If a test is negative, and we find that we think that somebody still has COVID, we’re going to send the PCR the same day,” she said.
Likewise, if people have mild symptoms but test negative under the antigen test, Fruth said they’d recommend that the patients self-isolate for a few days to see if they get better. If symptoms have worsened after two days, Fruth said they should return to get the PCR test.
“(The rapid antigen test’s) definitely going to have some good value,” she said. “It just has limitations. We don’t want people to be angry when we say, ‘Well, we can’t do the test for you if you don’t have symptoms,’ and we don’t want people to lie and say they have symptoms just because they want the test.”
To get tested at Avance Care’s Chapel Hill location, people can make testing appointments online or call (919) 590-9005.
Reporter Victoria Johnson can be reached at firstname.lastname@example.org.