Which COVID-19 test should you take?
47ABC – As we move through the holiday season many people may want to get a rapid test before they decide to travel, but before you take one of those rapid tests medical professionals want you to know a few things about them and that starts with knowing the difference between a molecular test and an antigen test.
The antigen test is what some consider the ‘rapid’ test because results can be delivered in as little as 15 minutes. However health professionals say a better way to refer to the two main types of diagnostic tests are to refer to them as ‘molecular’ testing which is polymerise chain reaction testing or PCR for short and Antigen testing. That’s because in some cases you can get results from a molecular test the same day, so using the term ‘rapid’ can be subjective.
So let’s start by explaining PCR or molecular testing and how it works.
According to the Food and Drug Administration a molecular test detects the virus’s genetic material. As Beth Prouse, a clinical microbiologist for TidalHealth Peninsula Regional explains they do so by taking a closer look at the nucleic acid collected.
“We amplify that nucleic acid before we start to try to detect it. So they’re very sensitive tests that we do in the clinical microbiology lab. We can detect just a few strands of the virus,” Prouse says.
The molecular test is the ‘gold standard’ as Prouse and many other medical experts put it. According to the FDA “the test is typically highly accurate and usually does not need to be repeated.”
Antigen ‘Rapid’ Testing
So what about Antigen testing? According to the FDA instead of looking for the virus’s genetic material like the molecular test, the antigen test looks for specific proteins from the virus.
With the antigen test, you can get results in as little at 15 minutes. However, the test doesn’t take as close of a look as the molecular test does.
“They’re not quite as sensitive as the tests we do in our clinical microbiology lab cause you’re not amplifying or making multiple copies of that material,” Prouse says.
According to the FDA, like the molecular test positive results with the antigen test are usually highly accurate. However unlike the molecular test there is a higher chance that false positives can happen, especially in areas where very few people have the virus. In some cases though negative results may need to be confirmed with a molecular test.
“Because if it’s a negative test and you’re symptomatic and it was an antigen test again you might need to follow that up with a molecular test,” Prouse says.
What if I’m asymptomatic?
That is where things get dicey, especially if you decide to take an antigen test. Prouse says that’s because if you’re asymptomatic you may just have low levels of the virus or the virus hasn’t started replicating to high amounts, which makes it harder to pick up on these antigen based tests.
At the end of the day, a molecular test would have the highest change of detecting someone who is asymptomatic.
As we said, health professionals consider the molecular test the ‘gold standard’ for a reason. So if you can get one, that’s your best bet. However if you are displaying symptoms of COVID-19 health professionals say it’s better to get either test than none at all.