Results
A total of 13,283 paediatric patients were included in our analysis. Females accounted for 45.8%. The median age was 6.8 years (IQR 3.0-11.2) and the most frequent age category was between 6 and 10 years (27.9%). The HS was the most frequent setting (66.9%), followed by the emergency department (20.9%). The overwhelming majority of the swabs were executed as NAAT (96.3%). Overall, 1,422 tested positive (10.7%), 11,771 tested negative (88.6%), 90 were indeterminate or missing (0.7%). The mean of pooled Rt in the 14 days preceding the swab had a median of 1.18 (IQR=0.90-1.37), with a minimum of 0.68 in December 2020 and a maximum of 2.16 in October 2020.
According to the chi-square tests, the swabs tested positive more frequently among children above 6 years of age. The HS was the setting that presented the higher percentage of positive swabs (Table 2). In addition, the mean of pooled Rt in the 14 days preceding the swab had a different distribution across the swabs’ results (Mann Whitney U test: <0.001), with a median of 1.31 (IQR=0.98-1.83) for children with a positive swab and a median of 1.18 (IQR=0.90-1.37) for those with a negative swab.
Focusing on the HS, females accounted for 53.6% and the most frequent age category was between 6 and 10 years old (31.6%). Compared with the other settings, the children and adolescents who accessed the HS were more frequently male and aged between 3 years and 13 years (Table 3). In addition, the mean of pooled Rt in the 14 days preceding the swab had a different distribution across the settings (Kruskall Wallis test p<0.001). Indeed, pairwise comparisons showed a different distribution of the Rt in the 14 days preceding the swab for the swab executed in the school hotspot setting (median 1.22, IQR 0.96-1.39) compared with the other settings (emergency department: median 1.05, IQR 0.89-1.31; DH: median 1.05, IQR 0.89-1.31; hospital wards: median 1.05, IQR 0.89-1.31). Last, Table 4 shows the multivariable models with a swab tested positive as outcome. The swabs executed in all the settings had a lower likelihood of resulting positive compared with the HS setting. Compared with adolescents aged between 14 and 19 years old, new-borns below 3 months and patients aged between 11 and 13 years old reported a higher probability of a swab tested positive. Instead, children aged between 3 months and 2 years and children aged between 3 and 5 years were less likely to result positive. The higher was the mean of pooled Rt in the 14 days preceding the swab, the higher was the likelihood of resulting positive. Compared with children who received the NAAT, those who received the RADT were less likely to test positive. Figure 1 shows the total number of swabs per week and number of swabs that tested positive per week (only school hotspot setting).