Performance of a SARS-CoV-2 antigen rapid immunoassay in patients admitted to the emergency department
Christian Leli, Luigi Di Matteo, Franca Gotta, Elisa Cornaglia, Daria Vay, Iacopo Megna, Rosalia Emanuela Pensato, Riccardo Boverio, Andrea Rocchetti
Abstract
OBJECTIVES: Given the ongoing pandemic emergency, there is a need to identify SARS CoV-2 infection in various community settings. Rapid antigen testing is spreading worldwide, but diagnostic accuracy is extremely variable. Our study compared a microfluidic rapid antigen test with a reference molecular assay in patients admitted to the emergency department (ED) of a general hospital from October 2020 to January 2021. METHODS: Nasopharyngeal swabs collected in patients with suspected COVID-19 and in patients with no symptoms suggesting COVID-19, but requiring hospitalization, were obtained. RESULTS: 792 patients of median age 71 years were included. With a prevalence of 21%, the results showed: 68.7% (95% confidence interval [CI]: 60.9-75.5) sensitivity; 95.2% (95% CI: 93.1-96.7) specificity; 79.2% (95% CI: 71.4-85.3) positive predictive value (PPV); 91.9% (95% CI: 89.5-93.9) negative predictive value; 3.8 (95% CI: 2.7-5.3) positive likelihood ratio (LR+); and 0.09 (95% CI: 0.07-0.1) negative likelihood ratio (LR-). In the symptomatic subgroup, sensitivity increased to 81% (95% CI: 70.3-88.6) and PPV to 96.9% (95% CI: 88.5-99.5), along with an LR+ of 32 (95% CI: 8.2-125.4). CONCLUSIONS: The new rapid antigen test showed an overall excellent diagnostic performance in a challenging situation, such as that of an ED during the COVID-19 emergency.