LOUISVILLE, Ky. — The U.S. government has one billion COVID-19 self-tests available for free and ready to ship for U.S. households.
With that news, many people may opt to take an antigen self-test versus a PCR test, given the convenience and faster results. However, the PCR test is still considered the gold standard for COVID-19 testing. Therefore, it’s important to know the differences between the two tests to choose which test is best to use depending on the situation.
The first time Bob Murphy got tested for COVID-19 was when he had the virus last year in February.
“I was in the hospital for seven days, and my doctor was good and got me out of there fast,” Murphy told Spectrum News 1 while waiting at a drive-thru testing site in Louisville to get his second COVID-19 test, ever. The reason is because Norton Healthcare requires a PCR COVID-19 test for patients prior to surgery, and Murphy was scheduled to have back surgery.
Murphy hasn’t tested for COVID-19 regularly because, as far as he is aware, he hasn’t been in contact with someone who has COVID-19. He also has had no symptoms, and he said he and his wife mainly stay at home.
After Murphy’s PCR test swab was collected, it was sent to one of Norton Healthcare’s labs to be analyzed, with final results available to Murphy to access within 24 to 48 hours. The logistics involved with a PCR test take a lot more work for Murphy and the healthcare system than taking an at-home COVID-19 antigen test, which gives results in 15 to 30 minutes. However, a PCR test is more sensitive at detecting COVID-19 compared to an antigen test.
“So the molecular tests, PCR [tests], detect the RNA that’s in the virus, the nucleic acid,” Norton Healthcare’s Chief of Microbiology, Alan Junkins explained. “So what they do is they take a little piece of RNA, and they multiply it many, many, many times over again so they can detect a much smaller quantity of virus.”
Antigen tests don’t analyze the RNA of COVID-19, like PCR tests. Antigen tests detect COVID-19 viral proteins, which makes the tests less sensitive.
“I think they are good tests,” Junkins said. “Their weakness is that it takes a lot more virus to be positive than it would on a molecular instrument [a PCR test]. It may take 1,000 times more virus before that’s going to be positive, that antigen test, so you have to kind of keep that in mind.”
A less sensitive test means a less expensive test. While antigen tests cost $5 to $50, a PCR test ranges from $75 to $100.
While an antigen test is easy enough to take at home, Junkins explained it’s important to take an antigen test when one has symptoms related to COVID-19.
“The viral load, the amount of virus that you have in your upper respiratory tract, is going to be the highest right about the time that you are getting symptoms”, he explained.
“If you take it too early, it’s gonna be negative, and, if you take it too late, it’s going to be negative; so the best time is right around when symptoms develop,” Junkins further explained.
According to the CDC, if one tests positive on a COVID-19 antigen self-test, they should follow proper COVID-19 infection protocols, such as 10-day isolation and contacting close contacts so they are aware of your result. If one thinks their positive test result is incorrect, contact a healthcare provider to determine whether additional testing is necessary.
If you’re symptomatic, and the antigen test is negative, Junkins said to wait one to two days and take the second COVID-19 antigen self-test in the box. If it’s negative again, then they recommend a PCR test for a definitive negative result.
If you’re asymptomatic but were exposed to COVID-19, and the antigen test is negative, Junkins said take a PCR test 5-7 days after exposure to confirm a negative result.
“Because, you know, that’s gonna be so much more sensitive. If you’re not developing symptoms, it may be because you’re just not getting much virus there in the first place,” Junkins told Spectrum News 1.
While Murphy can access a drive-thru PCR test easily, he said it’s comforting to have COVID-19 antigen tests on hand.
“That if I do need it, I don’t have to look for a place to go get a test. I could just do it at home,” Murphy said.
However, Murphy added he probably won’t test for COVID-19 often since he plans to still stay away from people.
Every U.S. home is eligible to order four at-home COVID-19 tests for free, and they usually ship in 7-12 days.
To order the free antigen COVID-19 self-tests or for more information, visit CovidTests.gov.
Junkins advises paying close attention to the instructions of a COVID-19 self-test, specifically on how to properly collect the specimen because a poorly collected one won’t give accurate results.