Unlike an antibody test, the rapid antigen test can directly detect the causative agentof COVID-19, the coronavirus SARS-CoV-2. Itdetects the proteins of the virus (theantigens). These can be found in pharyngeal swabswhen the virus is replicatingthere. The rapid antigen test is therefore similar to the PCR test, particularly sensitivein the initial phase of the infection. Similar to the PCR test, it can also indicate a virusinfection before symptoms appear.