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

Abstract

Introduction: 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. Methods: 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. Results: 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%e99.4%) concordance rate with real-time RT-PCR, along with a sensitivity of 86.7% (95% CI: 78.6%e92.5%) and a specificity of 100% (95% CI: 99.7%e100%). 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%e96.9%). Conclusion: 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.

Diagnostic performance and characteristics of anterior nasal collection for the SARS-CoV-2 antigen test: a prospective study

“…On the other hand, the QuickNavi-COVID19 Ag test provided 100% specificity in both the present study and our previous study 3 . Although it is necessary to verify whether similar results can be obtained in other settings, false positives should be avoided to prevent unnecessary additional testing and inappropriate isolation measures 15 .…”

“…Although paired comparison between different swab samples lacked in this study, our study demonstrated that anterior nasal samples provided a lower antigen test sensitivity than our previous study evaluating nasopharyngeal samples 3 . Nevertheless, this lower sensitivity of 72.5% may be acceptable since according to the reported systematic review, sensitivity of nasal swab was 86% in comparison to nasopharyngeal swab by RT-PCR 9 .…”

“…The sensitivity of antigen tests is largely influenced by the viral load in collected samples 10 – 13 . The QuickNavi-COVID19 Ag test could detect SARS-CoV-2 in almost all samples with Ct values < 30, and in 18.8% of samples with Ct values > 30 3 . The viral load may vary between collection sites 14 , and this study recognized the viral load of samples was significantly lower when they were collected from the anterior nasal cavity (Fig.…”

“…The diagnostic performance of antigen test of nasopharyngeal samples has been evaluated, and the reported specificity is consistently high > 97%, while sensitivity ranges from 0 to 94% 2 . We previously evaluated the performance of an antigen test, QuickNavi-COVID19 Ag (Denka Co., Ltd., Tokyo, Japan), using nasopharyngeal samples from 1186 participants 3 . The overall sensitivity and specificity were 86.7% (95% confident interval [CI] 78.6–92.5%) and 100% (95% CI 99.7–100%), respectively, and the sensitivity for symptomatic participants was 91.7% (95% CI 82.7–96.9%) 3 .…”

Preventing COVID-19 spread in closed facilities by regular testing of employees—An efficient intervention in long-term care facilities and prisons?

“…In the model false positive tests are ignored, reflecting high specificity. While originally only PCR tests had such quality, antigen tests have been substantially improved [45][46][47][48][49][50]. While PCR tests need to be processed in a lab, their antigen-based counterparts are available as rapid tests that return the test result after 5-20 minutes.…”