evidence: There are two types of virus tests available that can diagnose COVID-19: - Polymerase chain reaction (PCR) tests (also called Nucleic Acid Amplification Tests [NAATs]) detect the genetic material of the virus that causes COVID-19. The samples are usually sent to a laboratory for testing, and results are usually available in 1 to 3 days. There are also rapid PCR diagnostic tests that are run on specialized equipment on-site, for which the results are available in several minutes. PCR tests tend to be the most reliable tests, whether or not you have symptoms. - Antigen tests detect specific proteins on the virus that causes COVID-19. Antigen tests are rapid diagnostic tests, which means results are available in several minutes. Self-tests taken at home are antigen tests. These tests are not as reliable as PCR tests, especially if you do not have symptoms.