If your doctor has determined that you are in need of COVID-19 testing, he or she will choose the most appropriate type of test for your specific needs. However, there is comfort in knowing exactly what to expect when it's time for your test. This guide will explain the three types of COVID-19 tests that are currently in use.
1. Antigen Test
Antigen tests are sometimes called "rapid tests" because they provide faster results than other test methods. According to the CDC, most current antigen tests can provide results in as little as 15 to 30 minutes. Antigen tests detect the parts of a COVID-19 virus that provoke an immune response, the spike proteins that protrude from the virus' outer shell.
To perform a COVID-19 antigen test, a mucus sample is collected by swabbing the inside of the nose. The swab is then inserted into a tube containing a solution that will react to the sample if it contains COVID-19 antigens.
Antigen tests are useful because of their fast turnaround and low cost, but they have their limitations. Antigen tests are less accurate than other forms of COVID-19 testing, so they are most commonly used for screening rather than for diagnosis. Your doctor may recommend an antigen test if you are asymptomatic but have potentially been exposed to SARS-CoV-2 at home, school, or work.
2. Molecular Test
You may hear molecular COVID-19 tests alternatively referred to as "RNA tests" or "PCR tests." This is because molecular tests operate on human RNA and rely on a biochemical reaction called polymerase chain reaction, or PCR.
Molecular COVID-19 testing is the most accurate way to test for active infections. Like antigen tests, they are performed by first collecting a nasal swab from the patient. This sample is then sent to a lab, where a machine tests the RNA in the sample for nucleic acids that can be matched to SARS-CoV-2. The PCR reaction creates millions of copies of the virus's genetic material if it is present, which greatly reduces the chance of a false positive.
If an antigen test returns positive during a COVID-19 screening, a molecular test may next be used to confirm the diagnosis. Molecular tests are also often ordered to confirm the diagnosis of symptomatic patients who are highly likely to have COVID-19. Since the sample must be sent to a lab, molecular COVID-19 tests usually have a turnaround time of a few days.
3. Antibody Test
Antibody tests are unlike other types of COVID-19 testing because they are less effective for detecting active infections. Instead of testing for viral antigens or genetic material, these tests identify antibodies that the immune system produces to fight the virus.
Antibodies are detectable in the blood stream, so you must simply provide a blood sample for an antibody test. The sample is then sent to a lab, where it is added to a Petri dish containing COVID-19 antigens. After an enzyme is added, the antigens will clump together with any COVID-19 antibodies in the sample.
Antibody tests are useful for determining if a patient who is no longer sick has had COVID-19 in the past. Unfortunately, a positive antibody test doesn't mean you are now immune to COVID-19, because health officials cannot yet confirm that the presence of antibodies confers immunity. Antibody tests may be useful for diagnosing and treating any long-term health complications that arise from COVID-19, however.
Diagnosing and treating COVID-19 is an ongoing endeavor, and the variety of tests that are now available demonstrate the advances in medical technology that have been necessary to battle the disease. If you suspect you have been exposed to COVID-19, your doctor can arrange a test and answer any additional questions you may have.