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

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.

Evaluation and clinical implications of the time to a positive results of antigen testing for SARS-CoV-2

“…We expected DIA to have a higher sensitivity than QuickNavi™-COVID19 Ag because of its lower limit of detection and its implementation of a digital immunoassay system [ 8 ]. However, the two tests had almost identical sensitivity when used with clinical samples.…”

“…We previously evaluated the diagnostic performance of QuickNavi™-COVID19 Ag (Denka Co., Ltd., Tokyo, Japan), revealing a sensitivity of 86.7% and a specificity of 100% [ 7 ], with a read time of 15 minutes. The sensitivity seemed sufficient, although the limit of detection was inferior to that of a rapid immunochromatography, which utilizes a digital immunoassay (DIA) platform [ 8 ]. The head-to-head comparison using clinical samples has been awaited to validate their test performances.…”

Clinical evaluation of the rapid nucleic acid amplification point-of-care test (Smart Gene SARS-CoV-2) in the analysis of nasopharyngeal and anterior nasal samples

“…In this study, we enrolled participants and collected samples at the PCR center in Tsukuba Medical Center Hospital (TMCH) between March 25 and July 5, 2021, which intensively collected nasopharyngeal samples for the PCR analysis of SARS-CoV-2 [ [5] , [6] , [7] , [8] , [9] ]. Subjects referred by 59 primary care facilities and a local public health center, as well as TMCH healthcare workers with suspected SARS-CoV-2 infection based on symptoms or a known contact history with COVID-19 confirmed/suspected patients were prospectively enrolled.…”

“…For the evaluation of nasopharyngeal samples, we obtained one additional nasopharyngeal sample for the evaluation of Smart Gene SARS-CoV-2, as previously described [ 6 , 7 ]. For the evaluation of anterior nasal samples, we obtained two additional anterior nasal samples, as previously described [ 5 ], for the Smart Gene SARS-CoV-2 and reference real-time RT-PCR assays.…”

Analytical performance of the rapid qualitative antigen kit for the detection of SARS-CoV-2 during widespread circulation of the Omicron variant

“…Two nasopharyngeal samples were separately collected by medical professionals one for RT-PCR and the other for antigen testing, as previously described [ [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] ]. A nasopharyngeal sample was obtained from each nasal cavity.…”