2024 Volume 73 Issue 3 Pages 460-466
To diagnose coronavirus disease 2019 (COVID-19), quantitative antigen test is said to be less sensitive than PCR. We examined the clinical performance of a quantitative antigen test through sensitivity of the quantitative antigen test in the SARS-CoV-2 and setting of the indeterminant. There were 165 of whom were positive in the real-time PCR (PCR) using nasopharyngeal samples and 30 of whom were negative from January 2022 to March 2023. The quantitative antigen test showed a sensitivity of 79.4%, a specificity of 100%, a positive concordance of 100%, and a negative concordance of 46.9% compared with the PCR. We found a correlation between the Ct value of PCR and the cut off index (COI) value of quantitative antigen test (r = 0.956; p < 0.01). Sensitivity of the quantitative antigen test progressively declined from 100% in Ct <30 to 69.2–94.7% in Ct 32–<34 and then to 0–27.3% in Ct 34–40. When we set the indeterminant line of quantitative antigen test up as 0.9–1.0 COI, 0.8–1.0 COI and 0.7–1.0 COI, sensitivity of the quantitative antigen test has improved as expands the range of the indeterminant compared with no setting of the indeterminant. These results suggest that the SARS-CoV-2 quantitative test is competent enough to diagnose COVID-19, and improved setting of indeterminant makes it possible to be comparable sensitivity compared with PCR.
