By now you likely know someone who has had a COVID-19 test, or you may have had one yourself. If you had a test at Tryon Medical Partners, then you had the “super swab” that goes all the way up and back into your nose and nasal cavity. You likely had to wait about 30 hours for your results, unlike your neighbor who got results pretty quickly after a shallow nasal swab at a local pharmacy. Which test was more accurate? Were your results worth the wait?
Which test is best? When you should get a test? Why do some people have to isolate for 14 days, and others ten? Dr. Jennifer Womack helps demystify the five Ws of COVID-19 testing.
WHAT Test Goes WHERE?
“There are four main places we can look in your body for the DNA we know to be in the coronavirus molecule,” says Dr. Womack. “The front of your nose, the back of your nose, your throat, or your saliva.”
“When your sample is taken to the lab, they use a process called polymerase chain reaction, or PCR, to detect the presence of the virus’ genetic material,” explains Dr. Womack. “Getting a good sample is key to an accurate outcome, but so is the sensitivity and specificity of the particular test.”
The anterior nasal test involves inserting a small cotton swab half an inch up both nasal cavities. These tests are readily available at large pharmacy chain stores and results. These swabs may be rapid tests or they may be send-off PCR tests. The rapid tests can have results in as fast as ten minutes, which is helpful only if the test is positive because these tests have a lower sensitivity than the send-off tests.
“If you receive a negative result with this more rapid but less sensitive test, the manufacturer recommends that the test be followed-up with a send-off test that is more sensitive to be sure the rapid result isn’t a false negative,” says Dr. Womack. The send-off tests can take 24 hours or up to a few days to result, as they are sent to a specialized lab that does PCRs.
Slightly more invasive is the nasopharyngeal swab, which looks like a small pipe cleaner that is inserted up the nose and into the back of the nasal cavity (near the throat). Though Dr. Womack lovingly calls it the “brain picker,” the swab does not (nor can it) go near the brain.
“When performed by a skilled administrator, the test should not be painful and should feel as though you have gotten water up your nose,” says Dr. Womack.
The benefit of the nasopharyngeal test is that it is highly sensitive in its ability to detect a positive case, and features 100% specificity, meaning that there are no false positives. The nasopharyngeal tests used by Tryon Medical Partners results in 36 to 48 hours.
“With the relatively new saliva test, you chew on a wad of cotton that is then sent away to a lab,” says Dr. Womack. Just like the nasopharyngeal test, the saliva test is very sensitive and results are returned in a little more than a day. These tests are not yet widely available.
WHEN To Test?
The sensitivity of the test depends on when you get tested. Because COVID-19 tests measure genetic material, there have to be enough copies of the virus in your sample in order for the lab to detect it – which means that the virus needs time to make lots of copies before testing is done.
“If you start to feel symptoms then you will want to know immediately if you have it, but there’s no need to jump at a test,” says Dr. Womack. “Quarantine, give it two days and then get tested.” The sensitivity of the test is optimal on day three of symptoms; patients should be tested on day three whenever possible.
Exposed, asymptomatic patients should be tested no earlier than four days after exposure. Most patients who have been exposed will turn positive four to seven days after the exposure, but it can take up to 14 days after exposure for an exposed person to get sick.
“Please quarantine while you wait to get a test and while you wait for results,” adds Dr. Womack. “If you have a sick person in your house, isolate them to keep everyone else well.”
If you need a test in order to travel or to visit a sick relative, make sure to quarantine after your test and until you travel to prevent interim exposure to the virus.
WHY Do I Have to Wait?
Many people are understandably confused about how long they have to quarantine. Recommendations vary based on exposure and the long incubation period of the disease.
“We know that the virus is really only contagious for about ten days in most people,” said Dr. Womack. “So, in general, patients with a positive test need a ten-day quarantine.” Patients who have been exposed but have a negative test need a 14-day quarantine, because it can take up to 14 days after an exposure for someone to get sick.
WHO Do I Trust?
Because there is still much to learn about COVID-19, it can be hard to know what sources of information to trust. How do you know who or what to believe?
Here’s Dr. Womack’s advice: “Have a healthcare provider that you trust who knows you, and they can pass their best knowledge on to you.”