Reticular basement membrane (RBM) thickening may occur in children with allergic bronchial asthma (BA), cystic fibrosis (CF), and primary ciliary dyskinesia (PCD). Its functional consequences remain unknown. We investigated the relationship between baseline RBM thickness and subsequent spirometry. In our cohort follow-up study, patients aged 3-18 yr with BA, CF, and PCD and controls underwent baseline lung clearance index (LCI) measurement, spirometry, and endobronchial biopsy sampling. Total RBM and collagen IV-positive layer thickness were measured. Trends in forced vital capacity (FVC), forced expired volume in 1 s (FEV1), and FEV1/FVC were analyzed during follow-up, and their relationship to baseline characteristics was studied using univariate analysis and multiple regression models. Complete baseline data were available in 19 patients with BA, 30 patients with CF, 25 patients with PCD, and 19 controls. The RBM was thicker in patients with BA (6.33 ± 1.22 μm), CF (5.60 ± 1.39 μm), and PCD (6.50 ± 1.87 μm) than in controls (3.29 ± 0.55 μm) (all P < 0.001). The LCI was higher in patients with CF (15.32 ± 4.58, P < 0.001) and PCD (10.97 ± 2.46, P = 0.002) than in controls (7.44 ± 0.43). The median follow-up times were 3.6, 4.8, 5.7, and 1.9 years in patients with BA, CF, PCD, and controls, respectively. The z-scores of FEV1 and FEV1/FVC deteriorated significantly in all groups except in controls. In patients with CF and PCD, trends in FEV1 z-scores correlated with baseline LCI and RBM; in BA, it correlated with collagen IV. In multiple regression models, RBM morphology and ventilation inhomogeneity could predict up to 84.4% of variability in spirometry trends. In conclusion, baseline LCI value and RBM morphology may predict trends in subsequent spirometry.NEW & NOTEWORTHY This paper deals with the relationship between reticular basement membrane (RBM) morphology at baseline and follow-up spirometry in children with asthma, cystic fibrosis, and primary ciliary dyskinesia. For the first time, to our knowledge, the possibility to predict subsequent lung function development using selected baseline characteristics (reticular basement membrane morphology from endobronchial biopsy and ventilation inhomogeneity from nitrogen multiple breath washout test) is proposed. Corresponding predictive models are presented.

Department of Histology and Embryology 2nd Faculty of Medicine Charles University Prague Czech Republic

Department of Paediatrics 2nd Faculty of Medicine Charles University and University Hospital Motol Prague Czech Republic

Department of Probability and Mathematical Statistics Faculty of Mathematics and Physics Charles University Prague Czech Republic

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