Voldby C, Green K, Philipsen L, et al. - In this single-centre, randomised, controlled, parallel group study, researchers desired to know the degree of withdrawal of nebulised dornase alfa affected lung clearance index (LCI) in school-aged children with cystic fibrosis (CF) not receiving cystic fibrosis transmembrane conductance regulator modulators or hydrator therapy. They determined the effects of one month's withdrawal of nebulised dornase alfa (intervention) in 5-18 years old children with CF. Twenty-eight children (median age 10.4 [interquartile range: 7.6; 13.5] years) with CF received either standard care ( n = 14) or intervention ( n = 14). In school-age children with mild CF, withdrawal of dornase alfa for one month caused increasing ventilation inhomogeneity and deterioration of FEV ₁ and FEF _25–75. Therefore, by using LCI and spirometric parameters as endpoints, even in short-term clinical trials, adherence to dornase alfa has to be approached optimally.