Evaluation and Validation of the Roche Elecsys SARS-CoV-2 Antigen Electro-Chemiluminescent Immunoassay in a Southeast Asian Region

Abstract

Introduction: SARS-CoV-2 antigen tests can complement and substitute for RT-PCR tests. Centralized laboratory automated SARS-CoV-2 antigen tests that can be scaled to process a large number COVID-19 cases simultaneously are now available. We have evaluated the new Roche Elecsys SARS-CoV-2 antigen electro-chemiluminescent immunoassay. Methods: The Roche SARS-CoV-2 antigen assay is a double-antibody sandwich electro-chemiluminescent immunoassay, which reports a cut-off index (COI) (COI ≥ 1.0 considered positive). We assessed assay precision and linearity, and confirmed the reactivity limit. We determined the assay sensitivity and specificity with a verification group (289 controls and 61 RT-PCR positive COVID-19 cases). Assay performance was also validated against the consecutive samples we received (7657 controls and 17 cases) for SARS-CoV-2 antigen testing from June to October 2021. Result: The assay had a within-run precision CV of 3.0% at COI 0.68, and a CV of 1.5% at COI 3.49. Between-run precision was 3.0% at COI 0.68 and 1.8% at COI 3.49. The assay was linear from COI 0.65 to 7.84. All 35 C50 ± 20% test results performed over 7 days were positive/negative, respectively. In the verification group, overall sensitivity was 42.6% (26/61 positive, 95% CI 30.0–55.9), and specificity was 99.7% (1/289 positive, 95% CI 98.1–100). The agreement between the SARS-CoV-2 antigen and the RT-PCR cycle threshold (Ct) count was good (r = 0.90). In cases with Ct counts ≤ 30, the antigen assay sensitivity improved to 94.7% (18/19 positive, 95% CI 74.0–99.9). In our validation group, antigen sensitivity was 62.5% (5/8 antigen positive, 95% CI 24.5–91.5) within the first week of disease onset, but no cases were reactive after the first week of disease onset. Conclusion: The Elecsys SARS-CoV-2 antigen assay has good performance within manufacturer specifications. The sensitivity of the Roche antigen assay was greatest when used in patients with lower RT-PCR Ct values (≤30) and within the first week of disease onset.

Evaluation of four laboratory-based high-throughput SARS-CoV-2 automated antigen tests compared to RT-PCR on nasal and oropharyngeal samples

“…Three of the four AATs had similar analytical and clinical sensitivities, whereas the Liaison AAT from Diasorin had a significantly lower analytical and clinical sensitivity. This was unexpected, as previous studies evaluating each of the AATs have shown similar sensitivities [ 8 , 9 , 10 , 11 , 12 ]. Our findings highlight the need for comparison studies to allow direct comparison of different diagnostic tests.…”

Preparation of dyed polymer microspheres by a physical–chemical dual-binding method and their application in lateral flow immunoassay

“…If the COI value of the test sample is more than 1, it is considered positive; otherwise it is negative. 50 As shown in Fig. 7(a), the signal intensity of the test line was correlated with the COVID-19 virus N protein content of the sample.…”

“…If the COI value of the test sample is more than 1, it is considered positive; otherwise it is negative. 50 As shown in Fig. 7 S1, † the test values of each sample uctuated slightly around the average, and the coefficient of variations (CVs) were within 10%.…”

Combined Diagnosis of SARS-CoV-2: Rapid Antigen Detection as an Adjunct to Nucleic Acid Detection

“… 39 Using RT-PCR as a reference, the sensitivity was over 90% at Ct ≤ 30, and the sensitivity of the assay was higher within the first week of onset than after 1 week. 40 …”