Limited Sensitivity of a Rapid SARS-CoV-2 Antigen Detection Assay for Surveillance of Asymptomatic Individuals in Thailand.

COVID-19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is a global pandemic. Therefore, rapid and accurate tests for SARS-CoV-2 screening are urgently needed to expedite disease prevention and control especially in community transmission. Since late December 2020, Thailand has faced a new wave of COVID-19 outbreaks. The Thai National Disease Control program at the Ministry of Public Health has identified suitable measure for mass screening. A SARS-CoV-2 antigen-based assay is a surveillance option for active cases. Here, we evaluated the feasibility and test performance of a rapid SARS-CoV-2 antigen test during our field activities in 1,100 asymptomatic individuals in Samut Sakhon, Thailand, during the second wave COVID-19 outbreak (December 26-30, 2020). The results showed that the rapid antigen test had a sensitivity of 47.97% (95% CI: 36.10-59.96%) and a specificity of 99.71% (95% CI: 99.15-99.94%) versus standard reverse-transcriptase polymerase chain reaction. The rapid test performed better in cases with higher viral loads determined by the cycle threshold value. In real-world setting, the test performance can be compromised by several factors including viral loads, logistic chains, temperature, technical expertise of the operators, validity, and accuracy of the testing itself. Our study highlights a prerequisite for reevaluation of any given testing before implementing it at the national level.