Statistical approach to a definitive clinical trial of SDD in the PICU setting
HCAIs
RECRUITMENT
The potential recruitment rate for a future definitive cRCT was 3 children/site/week and was estimated by combining a potentially eligible population of 1730 children (estimated from nesting the screening log data from participating PICUs with the national UK PICU data from PICANet) and the overall proportion of eligible children recruited of 85%. This is very similar to the pre-trial estimated rate value of 3.0. The number of eligible children identified from screening logs in the six recruiting PICUs (434) was very similar to the estimate of potentially eligible children from PICANet for these PICUs (464).Assuming a parallel arm cluster-randomised design with a baseline period, the number of clusters per arm and overall sample size required to detect alternative treatment effects with 90% power and a significance level of 0.05 are shown in Table The only binary outcome with sufficient frequency to be potentially feasible was any positive microbiology result; however, a detectable difference in this outcome would need to be greater than would be delivered by prevention of all HCAIs. Suitable patient-centred outcomes include scale variables such as duration of mechanical ventilation or days alive and free of mechanical ventilation or length of PICU stay.Although the study was not powered to compare outcomes between groups, a summary of the potential outcome effects is shown in Supplementary Table 