Methods

We used databases from our previous study, where a retrospective chart review was performed of all endoscopic procedures (flexible bronchoscopy and flexible / rigid laryngoscopy, all under general anesthesia with spontaneous breathing) in pediatric patients with DS from April 2011 until June 2019. As a control group, we selected children without significant underlying disorder undergoing endoscopy for similar indications (selected from charts dating from January 2012 until January 2015).
In both groups, we checked for each patient whether a BAL sample for microbiological investigation was obtained during the endoscopic procedure. Of course this is only possible if a bronchoscopy was performed. If this was the case, results of cultures and / or PCR testing were listed. All positive cultures (even with small numbers of colony forming units per ml) were taken into account, in order to determine colonization. These results were subsequently categorized and compared by statistical analysis in SPSS. We used a Chi square test to compare the different categories of microbiological results and detect if the differences between both cohorts are statistically significant. The level of statistical significance was set at P ≤ 0.05.