Performance and Usefulness of a Novel Automated Immunoassay HISCL SARS-CoV-2 Antigen Assay Kit for the Diagnosis of COVID-19

Abstract Background: The aim of this study was to evaluate the clinical performance of a newly developed automated immunoassay HISCL SARS-CoV-2 Antigen assay kit designed to detect the nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: The HISCL SARS-CoV-2 Antigen assay kit is composed of automated chemiluminescence detection systems. Western blot analysis confirmed that anti-SARS-CoV antibodies detected SARS-CoV-2 N proteins. The best cut-off index (COI) was determined using human serum samples obtained from coronavirus disease-2019 (COVID-19) patients and patients without COVID-19. To test the clinical performance, 115 samples obtained from 46 patients with COVID-19 and 69 individuals who tested negative for COD-19 using reverse transcription quantitative polymerase chain reaction (RT-qPCR) were used. Results: The HISCL antigen assay kit showed a sensitivity of 95.4 % in the samples with copy numbers of >100, and a sensitivity of 16.6 % in the samples with copy numbers of <99. The kit did not cross-react with other human corona viruses causing seasonal common cold (HCoV 229E, OC43, NL63, and HKU1) and influenza (H1N1, H3N2, and B), and none of the 69 individuals with negative RT-qPCR results were diagnosed as positive. Importantly, 81.8 % of the samples with low virus load (<50 copy numbers) were diagnosed as negative. Thus, use of the HISCL antigen assay kit may reduce overdiagnosis compared with RT-qPCR tests. Conclusion: The rapid and high-throughput HISCL SARS-CoV-2 Antigen assay kit developed in this study can be used as a suitable screening test for infectious COVID-19, and may play a role in controlling the pandemic.