Effect of subjects’ demographic, clinical criteria and sampling time on the results of the RAT
Tables 3 and S2 show the diagnostic performance of the RAT in various subject’s subgroups. Although RAT results did not differ significantly between male and female subjects, it was slightly more sensitive and more accurate in female (sensitivity = 78.5% and accuracy = 79.4%) than in male (sensitivity = 76.1% and accuracy = 71.4%) participants and its specificity in female was almost twice (83.3%) that in male subjects (42.8%). High sensitivity and accuracy were evident when swabs were collected 0-7 days post-symptoms (n of subjects = 38) followed in order by the case when swabs were taken at 8-16 (n of subjects = 27) and >16 days post-symptoms (n of subjects = 4). There was no significant differences in the RAT results between symptomatic, radiology-positive subjects and asymptomatic, radiology-negative subjects, respectively. However, RAT was more sensitive and accurate in symptomatic subjects relative to the asymptomatic ones. RAT proved positive in 3 (60%) out of the 5 asymptomatic participants, one of these was considered asymptomatic COVID-19 carrier at the time of sampling as evidenced by the high RNA content (Ct = 17.6), showed strong positive RAT (i.e. strong line intensity) and showed symptoms 5-days after the sampling. RAT showed higher sensitivity and accuracy in subjects with no radiological findings than those with radiological findings. No radiological findings was evident in seven participants, 6 of whom were positive by both RAT and RT-qPCR.