Abstract Rationale Multislice computed tomography (MSCT) provides objective quantification of lung parenchyma through Hounsfield units (HU), yet correlation with comprehensive pulmonary function testing (PFT) remains insufficiently characterized in Latin American populations with chronic respiratory diseases (CRD). This knowledge gap limits optimal diagnostic integration and disease phenotyping strategies. Methods Retrospective cohort study analyzing 92 adult patients (≥18 years) with CRD at Omni Hospital, Ecuador (January 2020-April 2025). Patients underwent concurrent inspiratory-expiratory MSCT with HU quantification across six pulmonary regions and comprehensive PFT including spirometry, plethysmography, and DLCO. Primary outcome correlation between regional HU measurements and functional parameters. Secondary outcomes: HU thresholds for air trapping prediction, structure-function phenotype classification. Statistical analysis employed Pearson/Spearman correlations, multiple linear regression, and multivariate analysis controlling for age, sex, BMI, and smoking history. Results The cohort comprised 52% males, mean age 61.4 ± 12.3 years, 48% with COPD, 28% ILD, 24% other CRDs. Mean inspiratory HU demonstrated strong inverse correlation with FEV1 (r=-0.72, p 0.001) and moderate correlation with DLCO (r=-0.58, p 0.001). Expiratory-inspiratory HU difference (ΔHU) showed robust correlation with air trapping indices: residual volume/total lung capacity ratio (r = 0.81, p 0.001) and FEV1/FVC ratio (r=-0.69, p 0.001) (Figure 1A). Regional HU analysis revealed superior correlation in lower lung zones (r=-0.76) versus upper zones (r=-0.61). Optimal ΔHU threshold of ≤ 50 units predicted significant air trapping with 87% sensitivity and 82% specificity (AUC 0.91) (Figure 1B). Multivariable analysis identified ΔHU as independent predictor of functional impairment (β=-0.64, p 0.001) after adjusting for clinical variables. Three distinct structure-function phenotypes emerged: emphysema-predominant (low inspiratory HU, high ΔHU), fibrosis-predominant (high inspiratory HU, low ΔHU), and mixed pattern. Conclusions Quantitative MSCT analysis using inspiratory-expiratory HU measurements demonstrates clinically significant correlations with comprehensive pulmonary function parameters in CRD patients. The expiratory-inspiratory HU gradient emerges as a robust, objective imaging biomarker for air trapping and functional impairment severity. Regional HU heterogeneity provides insights into disease distribution patterns complementing traditional PFT. These findings support integration of quantitative CT into routine CRD evaluation, potentially reducing need for complex physiological testing while enabling precise disease phenotyping. The identified HU thresholds warrant validation in prospective multicenter cohorts to establish standardized imaging-functional assessment protocols in diverse CRD populations. This abstract is funded by: no funding
Briones-Zamora et al. (Fri,) studied this question.