Serum IL-6 and neutrophil elastase in paediatric bronchiectasis
Abstract
Background. Neutrophilic airway inflammation is a central pathogenic mechanism in bronchiectasis. However, the prognostic value of serum inflammatory biomarkers in the paediatric population remains uncertain, and most available evidence derives from mixed-etiology cohorts and adult patients. The aim of the study was to evaluate serum interleukin-6 (IL-6) and neutrophil elastase (NE/ELA2) concentrations in children with bronchiectasis of different etiologies, determine their diagnostic utility, and assess associations with key disease-control outcomes, including the rate of exacerbations requiring antibiotic therapy, hospitalisation frequency, forced expiratory volume in 1 second, and quality of life measured using bronchiectasis child-specific parent-proxy QoL instrument. Materials and methods. A total of 150 children aged 2–17 years were enrolled and divided into three groups: non-cystic fibrosis bronchiectasis (non-CF, n = 50), cystic fibrosis-associated bronchiectasis (CF, n = 50), and apparently healthy controls (n = 50). IL-6 and NE/ELA2 were measured by enzyme-linked immunosorbent assay. Kruskal-Wallis and Mann-Whitney tests, ROC analysis with area-under-the-curve (AUC) comparison using DeLong’s method, Spearman correlation, partial rank correlation, and Firth logistic regression were applied. Results. Both biomarkers exhibited a stepwise gradient: controls < non-CF < CF (all pairwise p < 0.001), and their distributions in patients and healthy controls did not overlap (AUC = 1.000). For clinically meaningful discrimination between etiological groups, performance was moderate: IL-6, AUC = 0.884; NE/ELA2, AUC = 0.865 (DeLong p = 0.653). In the pooled cohort, 21 significant correlations among 34 tested associations were identified, as well as 13 significant odds ratios among 18 evaluated comparisons (3.6–10.2). Conclusions. Serum IL-6 and NE/ELA2 reliably reflect disease presence and etiologic category. Within diagnostically homogeneous groups, however, their association with individual clinical course did not reach statistical significance, which — given the cross-sectional design — indicates limited prognostic value for monitoring and warrants confirmation in prospective studies. Based on the present data, disease monitoring should rely primarily on clinical outcomes and quality-of-life measures.