With the threat of the highly contagious Delta variant, even those who are fully vaccinated are wondering if the slightest cough could be COVID-19. As such, demand for COVID-19 testing has ramped up and some recommendations for when to test have been adjusted by the Centers for Disease Control and Prevention (CDC).
Dr. Jennifer Womack, an internal medicine specialist at Tryon Uptown, demystifies testing by sharing the five Ws of COVID-19 tests. Dr. Womack has been involved with testing and procedures at Tryon’s patient testing locations.
WHAT types of tests are available?
The most common tests are PCR tests (polymerase chain reaction) and antigen tests. PCR tests are more sensitive and specific than antigen tests and should be used instead of or in addition to antigen tests whenever possible.
“When your PCR test sample is taken to the lab, they use a process called polymerase chain reaction 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.”
If you use the more rapid but less sensitive antigen test antigen test and receive a negative result the manufacturer recommends that the test be followed-up with a PCR test that is more sensitive to be sure the rapid result isn’t a false negative.
“PCR testing is usually a send-off test in which you will have to wait a day or more for the results but there are some locations in Charlotte that offer rapid PCR testing,” Dr. Womack says. “Antigen testing is usually rapid and is also widely available. Most of the over-the-counter tests that you can buy and use at home are rapid antigen tests. If you are sick, I would recommend a PCR test as it is much more sensitive at detecting the virus.”
WHERE are the tests administered?
Both PCR and antigen tests collect fluid from the nasal cavity, the mouth or the throat depending on the type of test, and then look for pieces of the virus’ DNA (as in PCR testing) or particles of the virus’ “body” (as in the antigen test).
An anterior nasal test involves inserting a small cotton swab half an inch up both nasal cavities. These swabs may be rapid tests or they may be send-off PCR tests.
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.
Tryon Medical Partners is currently using the anterior nasal and nasopharyngeal swab tests.
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 the appropriate amount of time and then get tested.”
Exposed, asymptomatic patients who have been vaccinated should wear a mask and get tested three to five days after exposure. Once the test is negative, they can return to usual activities. Those who are unvaccinated and exposed to a sick person should quarantine at home and test immediately. If the test is negative, continue to quarantine and test again after five to seven days. If you are not vaccinated, even if you have a negative test, the recommendation is to continue the quarantine for 10 to 14 days after the exposure since the virus has a long incubation period.
“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?
PCR tests are the most sensitive after about 72 hours of symptoms. Testing done in the first one to two days of symptoms can often have false negative results since the virus is still multiplying and may not be at high numbers yet inside your body.
“You can certainly do a test on the first day of symptoms,” Dr. Womack says. “But if you are having typical COVID symptoms and have a negative test on the first day or two, consider staying home and doing another test after about two to three days of symptoms.”
You should always stay home and quarantine if you are sick while you are waiting for your results. If you are vaccinated and receive negative results, you can return to usual activities. If you are not vaccinated, even if you have a negative test, continue the quarantine for 10 to 14 days after the exposure since the virus has a long incubation period.
If you have a positive test, quarantine is 10 days at a minimum. Day one is the first day you have symptoms. Be sure your symptoms are consistently improving and you have no fever for one to two days before ending the quarantine on day 11. If you are continuing to have symptoms after the initial 10 days, extend your quarantine until you have had consistent improvement for one to two days.
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.”