Diagnostic tests for current infection: If you want to know if you are currently infected with the COVID-19 virus, there are two types of tests: molecular tests and antigen testing.
MOLECULAR TEST (also called PCR tests, viral RNA tests, nucleic acid tests)
How is it done? Nasal swabs or throat swabs
Where can you get this test? At a hospital, in a medical office, drive-by testing stations (will be available at the Pitzer campus)
What does the test look for? Molecular tests look for genetic material that comes only from the virus.
How long does it take to get results? It depends on lab capacity. Results may be ready the same day, but usually take at least a day or two. Throughout the pandemic, especially lately, delayed turnaround times of up to a week or two have been reported in many places.
What about accuracy? False negatives — that is, a test that says you don’t have the virus when you actually do have the virus — may occur. The reported rate of false negatives is as low as 2% and as high as 37%.
A molecular test using a deep nasal swab is usually the best option, because it will have fewer false negative results than other diagnostic tests or samples from throat swabs or saliva.
How is it done? A nasal or throat swab.
Where can you get these tests? At a hospital or doctor’s office.
What does the test look for? This test identifies protein fragments (antigens) from the virus.
How long does it take to get results? The technology involved is similar to a pregnancy test or a rapid strep test, with results available in minutes.
What about accuracy? The reported rate of false negative results is as high as 50%, which is why antigen tests are not favored by the FDA as a single test for active infection.
Tests for past infection
ANTIBODY TEST (also called serologic testing)
How is it done? A sample of blood is taken.
Where can you get these tests? At a doctor’s office, blood testing lab, or hospital.
What does the test look for? These blood tests identify antibodies that the body’s immune system has produced in response to the infection. While a serologic test cannot tell you if you have an infection now, it can accurately identify past infection.
How long does it take to get results? Results are usually available within a few days.
What about accuracy? Having an antibody test too early can lead to false negative results. That’s because it takes a week or two after infection for your immune system to produce antibodies. The reported rate of false negatives is 20%. However, the range of false negatives is from 0% to 30% depending on the study and when in the course of infection the test is performed.
Research suggests antibody levels may wane over just a few months. And while a positive antibody test proves you’ve been exposed to the virus, it’s not yet known whether such results indicate a lack of contagiousness or long-lasting, protective immunity.
Posted: Tuesday, February 9, 2021
Last Updated: Tuesday, February 9, 2021