The evaluation of a newly developed antigen test (QuickNavi™-COVID19 Ag) for SARS-CoV-2: A prospective observational study in Japan

Several antigen tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed worldwide, but their clinical utility has not been well established. In this study, we evaluated the analytical and clinical performance of QuickNavi™-COVID19 Ag, a newly developed antigen test in Japan. This prospective observational study was conducted at a PCR center between October 7 and December 5, 2020. The included patients were referred from a local public health center and 89 primary care facilities. We simultaneously obtained two nasopharyngeal samples with flocked swabs; one was used for the antigen test and the other for real-time reverse transcription PCR (RT-PCR). Using the results of real-time RT-PCR as a reference, the performance of the antigen test was evaluated. A total of 1186 patients were included in this study, and the real-time RT-PCR detected SARS-CoV-2 in 105 (8.9%). Of these 105 patients, 33 (31.4%) were asymptomatic. The antigen test provided a 98.8% (95% confidence interval [CI]: 98.0%–99.4%) concordance rate with real-time RT-PCR, along with a sensitivity of 86.7% (95% CI: 78.6%–92.5%) and a specificity of 100% (95% CI: 99.7%–100%). False-negatives were observed in 14 patients, 8 of whom were asymptomatic and had a low viral load (cycle threshold (Ct) > 30). In symptomatic patients, the sensitivity was 91.7% (95% CI: 82.7%–96.9%). QuickNavi™-COVID19 Ag showed high specificity and sufficient sensitivity for the detection of SARS-CoV-2. This test is a promising potential diagnostic modality especially in symptomatic patients.