As for other RAT, a previous study showed that STANDARD F COVID-19 Ag FIA is highly specific (98.4%, 95% CI: 96.0% to 99.6%) for SARS–CoV-2 Ag detection in NPS, and highly sensitive (95.2%, 95% CI: 76.2% to 99.9%) for those samples with Ct values lower than 25, which are harbored by patients with high viral load, who are more likely to be expected to be able to transmit the infection [14,16,17]. This evidence concerns the gene RENBP and infection.