Prospective analytical performance evaluation of the QuickNavi™-COVID19 Ag for asymptomatic individuals

Introduction: Antigen testing may help screen for and detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in asymptomatic individuals. However, limited data regarding the diagnostic performance of antigen tests for this group are available. Methods: We used clinical samples to prospectively evaluate the analytical and clinical performance of the antigen test QuickNaviTM-COVID19 Ag. This study was conducted at a PCR center between October 7, 2020 and January 9, 2021. Two nasopharyngeal samples per patient were obtained with flocked swabs; one was used for the antigen test, and the other for real-time reverse transcription PCR (RT-PCR). The diagnostic performance of the antigen test was compared between asymptomatic and symptomatic patients, and the RT-PCR results were used as a reference. Results: Among the 1934 collected samples, 188 (9.7%) demonstrated detection of SARS-CoV-2 by real-time RTPCR; 76 (40.4%) of these 188 samples were from asymptomatic individuals, and over half of the total samples were asymptomatic (1073; 55.5%). The sensitivity of the antigen test was significantly lower for the asymptomatic group than for symptomatic patients (67.1% vs. 89.3%, respectively, p < 0.001). The specificity was 100% for both groups, and no false positives were observed among all 1934 samples. The median cycle threshold value for the asymptomatic group was significantly higher than that of the symptomatic group (24 vs. 20, p < 0.001). Conclusions: The QuickNaviTM-COVID19 Ag showed lower sensitivity for the asymptomatic group than for symptomatic patients. However, its specificity was consistently high, and no false positives were found in this study.