RT-PCR tests work by detecting bits of viral genetic material present in a patient’s mucus, saliva and cells at the very back of their nasal cavity, where the nose meets the throat. This test involves the administration of a nasal swab that will capture mucus and secretions from your nose. This procedure is called a nasopharyngeal swab and is used to identify upper respiratory infections. These tests can recognize if someone has any COVID-19 viral genetic material in their body. This means that someone has or had COVID-19.