Comparison between the Sofia SARS Antigen FIA Test and the PCR Test in Detection of SARS-CoV-2 Infection

Objective The purpose of this study was to compare Quidel’s rapid antigen test Sofia SARS antigen Fluorescent Immunoassay (FIA) (Sofia) with the real-time reverse transcription–polymerase chain reaction (rRT-PCR) test. Methods Two samples were taken from each test subject—1 for testing with the Sofia test and 1 for testing with the rRT-PCR test. In total, swabs were taken from 146 subjects who presented symptoms of infection (group 1) and 672 subjects who were tested regardless of symptoms (group 2). Results In group 1, the sensitivity of the antigen test was 90.0% and its specificity 97.5%. In group 2, however, the sensitivity of the antigen test was 81.4% and the specificity 98.9%. In addition to asymptomatic patients, false-negative results of rapid antigen tests also occurred in subjects with high threshold values (cycle threshold > 30). Conclusion Our results show that the Sofia test meets the standards for diagnostic tests according to the criteria of the World Health Organization, as they show high sensitivity and specificity, and perhaps most importantly, a high negative predictive value (> 95%).