LAUSR

BACKGROUND Bronchial epithelial reticular basement membrane (RBM) thickening occurs in diseases with both eosinophilic [allergic bronchial asthma (AB)] and neutrophilic [cystic fibrosis (CF), primary ciliary dyskinesia (PCD)] chronic airway inflammation; however, lung function and airway remodelling relationship remains unclear. The aim of the study was to test whether ventilation inhomogeneity is related to RBM thickening. METHODS Multiple breath washout test, endobronchial biopsy, and bronchoalveolar lavage were performed in 24 children with CF, 11 with PCD, 15 with AB, and 19 controls. Lung clearance index (LCI2.5), RBM thickness, and lavage fluid cytology were quantified; their mutual relationships were studied using Spearman rank correlations (r). RESULTS In asthma, ventilation inhomogeneity was mild (LCI2.5 9.3±1.4, versus 7.9±0.9 in controls, p=0.0391, data shown as mean±standard deviation) and RBM thickened (5.26±0.98 μm, versus 3.12±0.62 μm in controls, p<0.0001). No relationship between RBM thickness and ventilation inhomogeneity or lavage cytology was found. In CF and PCD, RBM thickness was similar to that in asthma (4.54±0.66 μm and 5.27±1.11 μm, respectively), ventilation inhomogeneity was significantly higher (LCI2.5 12.5±2.4 and 11.8±2.5, respectively). Both in CF and PCD, RBM thickness correlated with LCI2.5 (r=0.594, p=0.015; r=0.821, p=0.023, respectively). In PCD only, RBM thickness was also related to the number of neutrophils in lavage fluid (r=0.821, p=0.023). CONCLUSIONS Lung function impairment in relation to RBM thickness was milder in AB than in CF and PCD. In asthma, ventilation inhomogeneity did not correlate with RBM thickness while in CF and PCD it did. This suggests different structure-function relationship in these diseases.