What is a COVID diagnostic test?
A diagnostic test is used to detect the presence of the virus or parts of the virus in the sample obtained from the person. For the SARS-CoV-2 virus, diagnostic tests are performed on a sample from the respiratory tract, such as the nasopharynx (the upper part of the throat behind the nose), the nose, or throat, or from saliva.
What’s the difference between what’s known as the PCR test and the rapid tests? Is one type more accurate?
The polymerase chain reaction (PCR) and nucleic acid amplification tests (NAATs) are molecular tests. Molecular tests detect the presence of the virus’s genetic material, known as RNA. In general, these tests are considered to be the “gold standard” for diagnosis of COVID-19. They have greater sensitivity than antigen tests, meaning they can detect more people who have COVID-19 infection.
Antigen tests, also known as rapid tests, detect the presence of one or more proteins that are part of the virus. Antigen test results can be acquired quickly because they require less complex technology. They frequently have a faster turnaround than molecular tests, and some can be done at a doctor’s office or clinic.
Because antigen tests have lower sensitivity, a false negative result is possible. This is important because a negative antigen test does not necessarily mean you don’t have the virus. If you have reason to suspect you were exposed, such as having symptoms of COVID-19 or live in a setting in which there is an ongoing outbreak, it’s recommended you confirm the result with a PCR test. It is also important to note that a negative test (either antigen or PCR test) immediately following an exposure to someone with COVID-19 does not prove you were not infected, because it can take several days for the virus to become detectable.
When should people get a test?
While specific recommendations vary among local and state health departments and other agencies and employers, groups prioritized for testing are people with symptoms of COVID-19 and those with known exposure to COVID-19. Other situations in which testing has been recommended include after traveling, after attending larger indoor gatherings, prior to invasive medical procedures and surgery, and for people who work or live in a long-term care facility or another congregate residential setting.