Q: Can you explain how the coronavirus test works?
A: There are actually several types of tests for COVID-19 that are either readily available today or that are entering stages of widespread mass production. The most reliable kind of available test checks to see if there is evidence of the virus in your respiratory system. The test is performed by swabbing the back of your nose for a sample that will be sent to a laboratory. A positive result for COVID-19 is returned if the genetic material (RNA) for coronavirus is detected. This kind of test is quite accurate and is the best test for diagnosing active cases of COVID-19. For that reason, it is the test most commonly performed.
However, this test does require expensive equipment usually found in a large, central laboratory. It takes four to six hours for the actual lab work, and after you factor in transportation of the specimen, a turnaround time of more than 24 hours can be expected. This is the type of testing used by the federal Centers for Disease Control and Prevention (CDC), the Tennessee state laboratory, most commercial labs and our own county lab at Baylor School.
Another type of test looks for antibodies to the virus. Antibodies are the proteins that your body develops to fight off a disease. A positive test for antibodies is good evidence that you have had COVID-19. But it takes time for antibodies to develop in the bloodstream, so this type of test is not as reliable early in the course of the disease and is not recommended to diagnose an active infection.
This type of test is also less reliable because it depends upon an active immune response to the disease. These antibody tests can be used to help identify people who have already had the disease, but at this point it is not known how much protection you might have from these antibodies after recovering from the disease or how long it might last. However, because the antibodies are already present in their blood, those who have recovered from coronavirus can donate their plasma to be used to treat other patients. The first test of this kind was approved by the FDA on April 1 and can be done with a finger-stick blood sample. Unfortunately, some of these tests coming out have been faulty, especially the “rapid tests,” and most have not been approved by the FDA.
If you feel like you need to be tested for COVID-19, drive-thru testing is available at the Vehicle Emission Testing Center at 7460 Bonnyshire Drive. Call 423-209-8393 to schedule an appointment. For any additional information or questions about COVID-19 you may have, call the Chattanooga-Hamilton County Health Department COVID-19 Hotline at 423-209-8383.
– Dr. Paul Hendricks, health officer, Chattanooga-Hamilton County Health Department; member, Chattanooga-Hamilton County Medical Society