A Look at COVID-19 Tests
By Eugenia Jones
There is a definite need for understanding the different types of tests used to detect the COVID-19 virus.
Basically, there are two primary types of COVID-19 tests: molecular tests (including PCR tests) and rapid antigen tests. A third type of test looks for antibodies to determine if you have already had the virus.
According to the pathologist Dr. Brian Rubin and the Cleveland Clinic website, Molecular COVID-19 tests, usually performed by testing a swab specimen from the nose, are more sensitive and specific than rapid antigen tests. The PCR test is a type of molecular test and is capable of finding low levels of the viral RNA. However, the molecular PCR test must be sent to a lab for results which takes a longer amount of time than the antigen test-usually at least 24 hours.
Antigen tests are rapid tests capable of giving results in fifteen minutes and do not require a lab. According to the Cleveland Clinic, antigen tests are able to detect virus in highly infectious patients which can assist with isolation and quarantine procedures. However, the antigen test is not as sensitive as the molecular PCR test so false negatives are more likely especially when a patient is tested a week or longer after the onset of symptoms.
In contacting some of the medical offices throughout McCreary County, “The Voice” found most offices use both types of tests. South Fork Medical Clinic reported using both types of COVID-19 tests as did Hope Primary Care. At Hope Primary Care, practitioners routinely administer the molecular test requiring lab results if a false negative is suspected on the rapid test. At Appalachian Family Care, a finger prick rapid test and PCR test are normally administered together.
“If a good specimen is collected, the PCR test is the gold standard for COVID-19 testing,” Appalachian Family Care’s APRN Dustin Hamlin said. “The finger prick test has an IGG (past infection) accuracy of about 98% and an IGM (current infection) accuracy of about 93%. That’s not bad for a rapid test but still indicates 7 out of 100 tests will come back false. That’s why we want patients to do both the rapid and PCR tests together. We do a finger prick rapid so patients don’t get their noses swabbed twice in the same visit.”
According to the Cleveland Clinic, there are reasons for a false negative COVID-19 test result including:
-Testing too early in the course of illness. The virus hasn’t multiplied enough to be detected by the test.
-A good specimen was not obtained.
-The COVID-19 test itself was not sensitive or specific enough to detect COVID-19.
All COVID-19 tests must meet standards, but no test is 100% sensitive and 100% specific for COVID-19. This is why there is always a possibility of “false negative” and “false positive” tests.
If you think you might have COVID-19 even if your test is negative, it’s best to follow the current CDC recommendation. Stay home for 10 days if you think you are sick. Stay six feet away from others (“social distancing”) and wear a cloth mask. Contact your healthcare provider if your symptoms worsen. Contact your healthcare provider when your symptoms improve – don’t decide on your own if it’s safe for you to be around others.
Sources:
https://health.clevelandclinic.org/different-types-of-covid-19-tests
https://my.clevelandclinic.org/health/diseases/21214-coronavirus-covid-19
