Detection of SARS-CoV-2 infection by rapid antigen test in comparison with RT-PCR in a public setting

Kronberg Jakobsen, K.; Schmidt Jensen, J.; Todsen, T.; Lippert, F.; Jean-Marie Martel, C.; Klokker, M.; von Buchwald, C.

Background: Rapid and accurate detection of SARS-CoV-2 infection is essential in limiting the spread of infection during the ongoing COVID-19 pandemic. The aim of this study was to determine the accuracy of the STANDARD Q COVID-19 Ag test (SD BIOSENSOR) by comparison with RT-PCR in a public setting. Method: Individuals aged 18 years or older who had booked an appointment for a RT-PCR test on December 26-31, 2020 at a public test center in Copenhagen, Denmark, were invited to participate. An oropharyngeal swab was collected for RT-PCR analysis, immediately followed by a nasopharyngeal swab examined by the STANDARD Q COVID-19 Ag test (SD BIOSENSOR). Sensitivity, specificity, positive and negative predictive values of the antigen test were calculated with test results from RT-PCR as reference. Results: Overall, 4697 individuals were included (female n=2456, 53.3%; mean age: 44.7 years, SD: 16.9 years); 196 individuals were tested twice or more. Among 4811 paired conclusive test results from the RT-PCR and antigen tests, 221 (4.6%) RT-PCR tests were positive. The overall sensitivity and specificity of the antigen test were 69.7% and 99.5%, the positive and negative predictive values were 87.0% and 98.5%. Ct values were significantly higher among individuals with false negative antigen tests compared to true positives. Conclusion: The sensitivity, specificity, and predictive values found indicate that the STANDARD Q COVID-19 Ag is a good supplement to RT-PCR testing.