SARS‐CoV‐2 rapid antigen test in comparison to RT‐PCR targeting different genes: A real‐life evaluation among unselected patients in a regional hospital of Italy

Abstract

We assessed the performance of the Panbio rapid antigen detection (RAD) test for the detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and we compared it with the routine reverse transcriptase‐polymerase chain reaction (RT‐PCR)‐based molecular test in a population of 4167 unselected patients admitted to IRCCS Sacro Cuore Don Calabria Hospital. Analysis stratified by cycling threshold (C t) value of SARS‐CoV‐2 gene targets indicated that antigen (Ag)‐positive C t values were significantly lower compared to Ag‐negative values (p < 0.0001). Overall, we found discordance in 140, tested negative by RAD and positive by RT‐PCR, and in 4 resulted positive by RAD and negative by RT‐PCR. RAD test achieved a sensitivity and specificity of 66.82% and 99.89%, respectively. The positive predictive value was shown to be 97.87% while the negative predictive value was shown to be 97.62%. In our context, the RAD test showed a reliable diagnostic response in subjects that displayed high C t values, corresponding to high viral load, while low ability was displayed to identify positive cases with medium‐low C t values, thus presenting low viral load and where confirmatory RT‐PCR was needed. Our finding supports the use of the RAD test in real‐life settings where a high volume of swabs is being processed but with caution when interpreting a positive test result in a low prevalence setting.