Lobe-based Quantitative CT Assessment of Emphysema in a Retrospective Multi-center COPD Cohort: Correlations with...

This study aimed to investigate the correlation between lobe-based Low Attenuation Area percentage (LAA%) and spirometric parameters in patients with Chronic Obstructive Pulmonary Disease (COPD), and to evaluate LAA% distribution patterns across different stages of COPD as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification.

A retrospective multi-center study was conducted involving 1,116 COPD patients who underwent non-contrast chest Computed Tomography (CT) and pulmonary function testing between December 2015 and December 2022. Patients were categorized into GOLD stages I-IV. CT images were analyzed using the FACT-Digital Lung™ software to quantify LAA% for each lobe and the whole lung. Group comparisons of LAA% and baseline characteristics were performed across GOLD stages. Correlations between LAA% and pulmonary function test parameters (FEV1% predicted and FEV1 /FVC) were assessed using Spearman's rank correlation test for unadjusted analyses and partial correlation (adjusting for age, sex, BMI, and smoking history) for adjusted analyses.

LAA% increased significantly as COPD progressed from GOLD II through GOLD IV across all lung lobes (P < 0.001), while no significant difference was found between GOLD I and II. The upper lobes consistently showed higher LAA% compared to lower lobes across all GOLD stages (P < 0.001). LAA% showed a significant inverse correlation with spirometric parameters. Stronger correlations were observed for FEV1 /FVC (r = -0.352 to -0.412) than for FEV1% predicted (r = -0.235 to -0.289), and all were significant (P < 0.001).

In this cross-sectional cohort, patients with early-stage COPD (GOLD I/II) showed significant functional impairment (reduced FEV1) without a corresponding significant increase in LAA% compared to GOLD I, whereas patients with moderate to severe COPD (GOLD III/IV) exhibited both functional impairment and elevated LAA%. This pattern is consistent with a dissociation between physiology and structure in early disease, and suggests that quantitative CT may be more sensitive to structural changes in advanced stages. However, due to the cross-sectional design, temporal relationships cannot be inferred.

Lobe-based quantification of LAA% effectively reflects the severity and regional distribution of emphysema and demonstrates significant associations with airflow limitation. These findings provide additional structural insights into COPD heterogeneity and support the value of quantitative CT as a complementary tool for assessing structural lung changes in patients with moderate-to-severe disease. Given the crosssectional design, the observed associations do not imply causality; prospective studies are needed to elucidate the temporal sequence and underlying mechanisms.