The overall sensitivity of the Panbio™ COVID-19 Ag rapid test device using nasal swab specimens was 64.7% (95% CI 47.9–78.5%). RATs have some benefits in screening, such as rapid identification of test results, low cost, and no requirement of instrument or expert skills [5,6,7, 11]. However, previous studies have reported that RATs using nasal swabs have lower sensitivity than that of RT-PCR. Peto et al. demonstrated that the sensitivity of RAT with nasal swabs using four different kits, including the Panbio™ COVID-19 Ag rapid test device, ranged from 78.8% as tested by laboratory scientists to 57.5% as tested by self-trained personnel . The results of our study are similar to those of previous studies. The results of RATs for the diagnosis of COVID-19 are available in < 15–30 min. In this study, the results were available within 10 min. Although there have been concerns that interpreting the RAT before or after a specified time could result in false-positive or false-negative test results, this was not observed in our study. Notably, the results of the Panbio™ COVID-19 Ag rapid test device did not differ from the initial interpretation despite the extended observation of 60 min.
Previous reports revealed that saliva specimens could be useful alternatives for detecting SARS-CoV-2 [3, 13, 14]. In a previous study, when compared with the RT-PCR results with NP swabs, the sensitivity and specificity of RT-PCR with saliva specimens were 85.19% and 89.19%, respectively, and the mean Ct value was 28.26 for NP swabs and 32.91 for saliva . Another study revealed that the sensitivity and specificity of RT-PCR with saliva specimens were 94.1% and 98.6%, respectively, and the median Ct values of NP swabs and saliva were 29.4 and 32.7, respectively . In our results, the sensitivity and specificity of RT-PCR using saliva specimens were 94.1% and 100.0%, respectively, and the median Ct values for NP swabs and saliva specimens were 18.5 (15.1–23.9) and 23.6 (17.9–29.4), respectively.
Although RT-PCR using NP swabs is considered the gold standard for diagnosing SARS-CoV-2 infection, it is not useful for repeated screening tests during school re-opening because of its long turn-around time and discomfort in acquiring NP specimens. Repeated rapid and non-invasive tests could be helpful for safe school re-opening. RATs using nasal swabs or RT-PCR using saliva specimens could be considered for repeated screening tests for COVID-19 . In this study, we evaluated the clinical performance of Panbio™ COVID-19 Ag rapid test device and RT-PCR test using self-collected saliva specimens for the detection of SARS-CoV-2 infection.
In conclusion, the sensitivity and specificity of the Panbio™ COVID-19 antigen rapid test device using nasal swabs and those of SSf-COVID19 kit using self-collected saliva specimens were 64.7% and 100% and 94.1% and 100%, respectively.