Statistical analyses
Statistical analyses were conducted using GraphPad Prism 9.5.0 (GraphPad Software, LLC). Pulmonary function parameters and their respective z-scores were expressed as means and standard deviations (SDs). The correlations between IOS and spirometric parameters were evaluated using Spearman’s rank correlation coefficient (ρ). The correlation was considered minimal when ρ was between 0 and 0.2, low when between 0.2 and 0.4; moderate between 0.4 and 0.6; good between 0.6 and 0.8; and very good between 0.8 and 1.
Pre- and post-BDR measures were compared using Wilcoxon signed-rank test, and differences between groups were evaluated using Mann-Whitney U-test.
To define the sensitivity and specificity of IOS parameters to detect an increase of 12% in FEV1, a receiver-operating characteristic (ROC) curve was plotted; cut-off levels were optimised using the Youden index (sensitivity + specificity - 1), and the accuracy was measured by the area under the ROC curve. A p-value of <0.05 was considered as statistically significant.