Lung clearance index is elevated in children and adolescents with bronchiectasis

<bold>Introduction:</bold> The lung clearance index (LCI) is a marker of ventilation inhomogeneity from the multiple breath washout (MBW) test. LCI is a sensitive marker of lung disease in children and adolescents with cystic fibrosis (CF) but has not been assessed extensively in children with non-CF bronchiectasis. We aimed to determine the clinical utility of LCI in children and adolescents with bronchiectasis. <bold>Methods:</bold> We compared MBW outcomes in children and adolescents with bronchiectasis (n=18; 10.7 ± 2.9 years, 56% male) to age- and sex-matched healthy controls (n=18) and children with CF (n=18). Nitrogen MBW data were collected using the Eco Medics Exhalyzer D device, analysed in Spiroware 3.3.1, and quality controlled according to international guidelines. Data are presented as mean ± standard deviation. <bold>Results:</bold> There were no differences in age, height, weight, body mass index, or sex between the groups (p > 0.05). LCI was significantly elevated (worse) in children and adolescents with bronchiectasis (7.6 ± 1.2) compared with healthy controls (6.5 ± 0.5; p=0.004). Mean LCI values were similar between children and adolescents with bronchiectasis and CF (7.0 ± 1.2; p = 0.2), however, the proportion of individuals with LCI values above the upper limit of normal (LCI > 7.1) was higher in those with bronchiectasis (61%) compared to CF (33%) (p < 0.05). <bold>Conclusion:</bold> The LCI is higher in children with bronchiectasis than in healthy controls, and a greater proportion of children with bronchiectasis have abnormal LCI than peers with CF. Next steps will be to examine relationships between LCI and markers of disease severity and assess how LCI changes over time in children and adolescents with bronchiectasis.