The two categories of COVID-19 tests are antibody tests and diagnostic tests.
Antibody tests help identify antibodies that indicate you’ve previously contracted the new coronavirus.
Antibodies are proteins that your immune system makes after mounting a successful immune response to the virus that causes COVID-19. Antibody tests can’t diagnose whether you currently have COVID-19.
Molecular tests and antigen tests are the two types of tests that can tell you if you currently have COVID-19. Molecular tests generally take longer but are more accurate.
Molecular tests (PCR tests)
Molecular tests go by several other names such as nucleic acid amplification (NAATs) and polymerase chain reaction (PCR) tests. They detect the DNA of the virus that causes COVID-19 to see if you’re currently infected.
When taken within 5 days of the onset of your symptoms, they correctly identify a positive test more than 90 percent of the time, if done within 5 days of symptoms, according to a 2020 study.
They’re considered the “gold standard” of testing, and many countries now require a mandatory PCR test within 48 to 72 hours before arrival.
However, the effectiveness of the test in identifying the presence of the new coronavirus quickly decreases to roughly 70-71 percent between days 9 and 11. By day 21, it’s dropped to around 30 percent.
During a PCR test, your doctor typically takes a swab of your nose and throat. The sample is then sent to a lab for processing.
Clinics that can process your results onsite may be able to provide you with your results within hours.
Clinics that have to send away for results — or clinics with a backlog of tests — may take a week or more to return your results.
Rapid PCR tests are now available, although there is some concern among healthcare professionals about their accuracy. These tests don’t need to be sent to a lab and can be performed at home.
Antigen tests (serological test)
Antigen tests, also called serological tests, attempt to detect certain proteins on the surface of the virus.
Compared to the PCR tests, they come with an increased risk of a false-negative, meaning that you may have the virus in your body, but your test shows that you don’t.
Your test is most likely to report a false-negative if the virus is present in low amounts.
Antigen tests are also referred to as rapid tests because some clinics can provide you results within minutes.
Since December 2020, the Food and Drug Administration has approved over-the-counter antigen tests for home use that can provide results in less than half an hour.
Antibody tests (PCR tests)
Antibody tests search for a previous infection. They can’t be used to diagnose a current infection because it can take 1 to 3 weeks after an infection develops for your body to make antibodies, according to the Centers for Disease Control and Prevention (CDC).
Generally, the test is done by pricking one of your fingers and collecting a drop of blood.
Some clinics may be able to give you your results on the same day, while other clinics may take several days.
According to the website of the private clinic CityMD, you can expect a 3- to 5-day wait to receive your results.