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.