Safe & easy to use rapid COVID testing kit. The Flowflex SARS-CoV-2 Antigen Rapid Test is a lateral flow chromatographic immunoassay for the qualitative detection of the nucleocapsid protein antigen from SARS-CoV-2 in nasal swab specimens directly from individuals who are suspected of an active COVID-19 infection by their healthcare provider within the first seven days of the onset of symptoms.