Performance Characteristics of a Rapid Severe Acute Respiratory Syndrome Coronavirus 2 Antigen Detection Assay at a Public Plaza Testing Site in San Francisco
Genay Pilarowski, Paul Lebel, Sara Sunshine, Jamin Liu, Emily Crawford, Carina Marquez, Luis Rubio, Gabriel Chamie, Jackie Martinez, James Peng, Douglas Black, Wesley Wu, John E. Pak, Matthew T. Laurie, Diane Jones, Steve Miller, Jon Jacobo, Susana Rojas, Susy Rojas, Robert M. Nakamura, Valerie Tulier-Laiwa, Maya Petersen, Diane V. Havlir, Joseph L. DeRisi
Abstract
We evaluated the performance of the Abbott BinaxNOW rapid antigen test for coronavirus disease 2019 (Binax-CoV2) to detect virus among persons, regardless of symptoms, at a public plaza site of ongoing community transmission. Titration with cultured severe acute respiratory syndrome coronavirus 2 yielded a human observable threshold between 1.6 × 104-4.3 × 104 viral RNA copies (cycle threshold [Ct], 30.3-28.8). Among 878 subjects tested, 3% (26 of 878) were positive by reverse-transcription polymerase chain reaction, of whom 15 of 26 had a Ct <30, indicating high viral load; of these, 40% (6 of 15) were asymptomatic. Using this Ct threshold (<30) for Binax-CoV2 evaluation, the sensitivity of Binax-CoV2 was 93.3% (95% confidence interval, 68.1%-99.8%) (14 of 15) and the specificity was 99.9% (99.4%-99.9%) (855 of 856).