SARS-CoV-2 Antigen Detection to Expand Testing Capacity for COVID-19: Results from a Hospital Emergency Department Testing Site

• Published in: Diagnostics (Basel) 2021-07, Vol.11 (7), p.1211
• Main Authors: Menchinelli, Giulia, De Angelis, Giulia, Cacaci, Margherita, Liotti, Flora Marzia, Candelli, Marcello, Palucci, Ivana, Santangelo, Rosaria, Sanguinetti, Maurizio, Vetrugno, Giuseppe, Franceschi, Francesco, Posteraro, Brunella
• Format: Article
• Language: English
• Subjects: antigen-based testing; Antigens; Asymptomatic; Biosensors; Coronaviruses; COVID-19; COVID-19 diagnostic tests; Disease transmission; emergency department; Hospitals; Immunoassay; Infections; Laboratories; molecular-based testing; Pandemics; Patients; Probability; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2
• ISSN: 2075-4418; 2075-4418
• DOI: 10.3390/diagnostics11071211

Background: SARS-CoV-2 antigen detection has currently expanded the testing capacity for COVID-19, which yet relies on the SARS-CoV-2 RNA RT-PCR amplification. Objectives: To report on a COVID-19 testing algorithm from a tertiary care hospital emergency department (ED) that combines both antigen (performed on the ED) and RT-PCR (performed outside the ED) testing. Methods: Between December 2020 and January 2021, in a priori designated, spatially separated COVID-19 or non-COVID-19 ED areas, respectively, symptomatic or asymptomatic patients received SARS-CoV-2 antigen testing on nasopharyngeal swab samples. Antigen results were promptly accessible to guide subsequent, outside performed confirmatory (RT-PCR) testing. Results: Overall, 1083 (100%) of 1083 samples in the COVID-19 area and 1815 (49.4%) of 3670 samples in the non-COVID-19 area had antigen results that required confirmation by RT-PCR. Antigen positivity rates were 12.4% (134/1083) and 3.7% (66/1815), respectively. Compared to RT-PCR testing results, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of antigen testing were, respectively, 68.0%, 98.3%, 88.8%, and 94.1% in the COVID-19 area, and 41.9%, 97.3%, 27.3%, and 98.6% in non-COVID-19 area. Practically, RT-PCR tests were avoided in 50.6% (1855/3670) of non-COVID-19 area samples (all antigen negative) from patients who, otherwise, would have needed antigen result confirmation. Conclusions: Our algorithm had value to preserve RT-PCR from avoidable usage and, importantly, to save time, which translated into a timely RT-PCR result availability in the COVID-19 area.