Discordant definitions of small airway dysfunction between spirometry and parametric response mapping: the HRCT-based study

Chen et al. investigated small airway dysfunction (SAD) using spirometry and parametric response mapping (PRM) with high-resolution CT (HRCT). The study assessed 388 participants, defining SAD through spirometry if two out of three flow rates (MMEF, FEF50%, FEF75%) were below 65% of predicted values, and through PRM when functional small airway disease (PRMfSAD) exceeded 20%. AVIEW software automated HRCT analysis, quantifying airway morphology and pulmonary vessel metrics. Spirometry-SAD correlated with thicker airway walls, smaller lumen, and reduced branch counts, while PRM-SAD showed subtle vessel-level differences. Predictive models combining HRCT features, such as bronchial wall thickness and emphysema volume, achieved high accuracy (AUC: 0.855 for spirometry, 0.808 for PRM). This research highlighted distinct mechanisms of SAD detection, with spirometry focusing on airway structure and PRM sensitive to early pulmonary dysfunction. The findings support integrating imaging tools for comprehensive SAD evaluation and enhancing early detection strategies.