Clinical sensitivity of rapid antigen test during a COVID-19 outbreak in Taipei, May to June 2021.

BACKGROUND/PURPOSE: This population-based study aimed to compare the accuracy of Rapid antigen detection (RAD) and reverse transcription-polymerase chain reaction (RT-PCR) assays for diagnosing individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the COVID-19 outbreak in Taipei, from May to June 2021. METHODS: In response to the outbreak of COVID-19 in mid-May 2021, Taipei City Hospital set up 12 citywide proactive community testing (PCT) stations for early identification of infected individuals from May 17 to June 20, 2021. Individuals with RAD positivity were isolated and later confirmed by RT-PCR. The c-statistic value was estimated to indicate the level of diagnostic accuracy of RAD tests. RESULTS: Of the 33,798 individuals who were evaluated for SARS-CoV-2 infection, 4.4% tested positive for RAD. There was a moderate concordance (kappa = 0.67) between the RAD tests and RT-PCR assay for identifying infectious individuals. The c-statistic value of the RAD test for the diagnosis of SARS-CoV-2 infection was 0.8. There was a positive linear trend between the accuracy of the RAD tests and the prevalence of SARS-CoV-2 infection in the study population (ß = 0.04; p = .03). As the cycle threshold value decreased, the sensitivity rate of the RAD tests increased (p < .001). After implementation of the PCT program, the prevalence of COVID-19 decreased from 8.4% to 3.3% (p < .001). CONCLUSION: Proactive community testing for SARS-CoV-2 infection using RAD tests could rapidly identify and quarantine the most infectious patients in the early phase of COVID-19 outbreak.