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Observational Study
. 2021 Oct;27(10):1493-1497.
doi: 10.1016/j.jiac.2021.07.006. Epub 2021 Jul 13.

The evaluation of a novel digital immunochromatographic assay with silver amplification to detect SARS-CoV-2

Yoko Kurihara  1 , Yoshihiko Kiyasu  2 , Yusaku Akashi  3 , Yuto Takeuchi  1 , Kenji Narahara  4 , Sunao Mori  4 , Tomonori Takeshige  4 , Shigeyuki Notake  5 , Atsuo Ueda  5 , Koji Nakamura  5 , Hiroichi Ishikawa  6 , Hiromichi Suzuki  7
Affiliations
Observational Study

The evaluation of a novel digital immunochromatographic assay with silver amplification to detect SARS-CoV-2

Yoko Kurihara et al. J Infect Chemother. 2021 Oct.

Abstract

Introduction: Rapid antigen tests are convenient for diagnosing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, they have lower sensitivities than nucleic acid amplification tests. In this study, we evaluated the diagnostic performance of Quick Chaser® Auto SARS-CoV-2, a novel digital immunochromatographic assay that is expected to have higher sensitivity than conventional antigen tests.

Methods: A prospective observational study was conducted between February 8 and March 24, 2021. We simultaneously obtained two nasopharyngeal samples, one for evaluation with the QuickChaser® Auto SARS-CoV-2 antigen test and the other for assessment with reverse transcription PCR (RT-PCR), considered the gold-standard reference test. The limit of detection (LOD) of the new antigen test was compared with those of four other commercially available rapid antigen tests.

Results: A total of 1401 samples were analyzed. SARS-CoV-2 was detected by reference RT-PCR in 83 (5.9%) samples, of which 36 (43.4%) were collected from symptomatic patients. The sensitivity, specificity, positive predictive value, and negative predictive value were 74.7% (95% confidence interval (CI): 64.0-83.6%), 99.8% (95% CI: 99.5-100%), 96.9% (95% CI: 89.2-99.6%), and 98.4% (95% CI: 97.6-99.0%), respectively. When limited to samples with a cycle threshold (Ct) < 30 or those from symptomatic patients, the sensitivity increased to 98.3% and 88.9%, respectively. The QuickChaser® Auto SARS-CoV-2 detected 34-120 copies/test, which indicated greater sensitivity than the other rapid antigen tests.

Conclusions: QuickChaser® Auto SARS-CoV-2 showed sufficient sensitivity and specificity in clinical samples of symptomatic patients. The sensitivity was comparable to RT-PCR in samples with Ct < 30.

Keywords: COVID-19; Digital immuno-chromatographic antigen test; FUJI DRI-CHEM; QuickChaser Auto; SARS-CoV-2; Silver amplification.

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Conflict of interest statement

Mizuho Medy provided fees for research expenses and provided the Quick Chaser® Auto SARS-CoV-2 without charge. Kenji Narahara, Sunao Mori, and Tomonori Takeshige are employed by Mizuho Medy, the developer of the Quick Chaser® Auto SARS-CoV-2. Hiromichi Suzuki received consultation fee from Mizuho Medy, and Fujifilm.

Figures

Fig. 1
Fig. 1
Difference in sensitivity of QuickChaser® Auto SARS-CoV-2 stratified by the day after symptoms onset. Two patients with unknown onset dates were excluded. White circles indicate positive samples, and black circles indicate negative samples for the antigen test.
See this image and copyright information in PMC

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