Abstract
In hospital practice, the use of the antigen quantitative test for the diagnosis of symptomatic patients suspected of having COVID-19 and screening for asymptomatic pathogen carriers must be considered separately. We examined the effectiveness of and the problems encountered with the use of the antigen quantitative test in two groups: symptomatic patients suspected of having COVID-19 and asymptomatic pathogen carriers. There were 277 symptomatic patients suspected of having COVID-19 and 1,781 asymptomatic patients who underwent both the RT-PCR test and SARS-CoV-2 antigen quantitative test on the same day from November 2020 to May 2021. A retrospective analysis was performed on a total of 2,058 samples. In the symptomatic patients suspected of having COVID-19, when the antigen level obtained was ≥ 0.36 pg/mL indicating positivity for SARS-CoV-2, the antigen quantitative test used for diagnosis showed a sensitivity of 95.9% and a specificity of 80.4%. In the asymptomatic patients, when the antigen level obtained was ≥ 0.83 pg/mL, the antigen quantitative test used for screening showed a sensitivity of 100% and a specificity of 99.5%. In this analysis, the antigen quantitative test was found to be extremely effective for screening for asymptomatic individuals. On the other hand, when the test is used for the purpose of diagnosing symptomatic patients, its sensitivity and specificity are slightly reduced. Therefore, it is necessary to fully understand its characteristics and make a comprehensive judgment based on a combination of clinical symptoms, diagnostic imaging, PCR tests, and antibody tests.
