Detection of COVID-19 Patients through SARS-CoV-2 Antigen Assay using Chemiluminescence Immunoassay: Comparison to RT-PCR Method

Background: Accurate and reliable diagnostic tools are essential in effectively managing infectious diseases during the ongoing global COVID-19 pandemic. For this study, the RT-PCR assay was used as the reference method, and the objective was to determine the concordance rate, sensitivity, and specificity of the SARS-CoV-2 antigen assay (SARS-CoV-2 Ag) using the chemiluminescence immunoassay (CLEIA) technique for identifying COVID-19 patients. Method: A total of 231 nasopharyngeal swab samples were collected from individuals with either COVID-19 (cycle threshold (Ct) values ≤ 40) or non-COVID-19 (Ct values > 40 or undetected) diagnoses. These samples were examined using the SARS-CoV-2 Ag. Results: The overall concordance rate of the SARS-CoV-2 Ag was 84.0% (194/231), with a sensitivity of 81.4% (162/199) and 100% specificity (32/32). When samples were categorized into two Ct value groups, the SARS-CoV-2 Ag demonstrated a sensitivity of 97.6% for samples with a Ct value ≤ 30 and 2.9% for samples with a Ct value > 30. Moreover, the antigen concentration determined by the SARS-CoV-2 Ag showed a strong inverse correlation with the Ct value obtained from the RT-PCR assay (r = -0.93, p < 0.001). Conclusion: The SARS-CoV-2 Ag proves to be a potentially effective tool for diagnosing and monitoring COVID-19 patients, particularly in settings where the RT-PCR assay is not available.