Speed versus sensitivity: Performance of SARS-CoV-2 rapid antigen test in the hospital setting

Background: As the world battles the coronavirus disease 2019 (COVID-19) pandemic, rapid detection is the key to contain the spread of the disease. Although real-time polymerase chain reaction (RT-PCR) remains the gold standard for the diagnosis of severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) infection, it demands specialized equipment and technical expertise. SARS-CoV-2 rapid antigen detection test (RAT) is the user-friendly alternative, which needs evaluation in the hospital setting. Materials and Methods: This cross-sectional study was carried out at the Indian Council of Medical Research approved COVID-19 diagnostic molecular laboratory between November and December 2020. Nasopharyngeal swabs in viral transport medium (VTM) were received from suspected SARS-CoV-2 infected individuals were processed for SARS-CoV-2 RT-PCR and a rapid antigen detection test, COVID-19 Ag Respi-Strip. Results: A total of 342 samples were assessed for this study by RT-PCR and Rapid Antigen Test. The sensitivity of RAT was found to be 41% at an RT-PCR cycle threshold of 35 or below. Sensitivity of RAT improved to 81.2% when a RT-PCR cycle threshold of 25 or below was considered as positive. Specificity of RAT was 99% to 100%. Conclusion: Rapid antigen test is a cost-effective alternative for screening of symptomatic individuals in the hospital setting. However, due to low sensitivity, the negative results need to be interpreted with caution