Flowchart of nasopharyngeal swab samples from patients triaged to COVID-19 or non-COVID-19 areas of the ED. Samples were tested for SARS-CoV-2 antigen with the SD Biosensor STANDARD F COVID-19 Ag FIA, yielding positive or negative results. Antigen results were compared with those obtained by RT-PCR for cases (1083 in the COVID-19 area, and 1815 in the non-COVID-19 area) in which confirmatory RT-PCR testing (performed within few hours from antigen testing) was required. Abbreviations: ED, emergency department; FIA, fluorescent immunoassay; COVID-19, coronavirus disease 2019; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; and RT-PCR, reverse-transcription polymerase chain reaction.