Correlation of Pulmonary Function Tests with Conventional & Caliper-Based Quantitative HRCT Analysis in Interstitial Lung Diseases

Introduction: Interstitial lung diseases (ILDs) are diffuse parenchymal lung disorders characterized by inflammation and fibrosis. HRCT and pulmonary function tests are key to disease assessment, while CALIPER-based Lung Texture Analysis provides objective quantification of disease burden. Aim & Objective: This study aimed to evaluate the correlation between HRCT findings and pulmonary function parameters and compare conventional radiologist-based HRCT assessment with CALIPER-derived quantitative analysis. Materials & Methods: This prospective, observational, cross-sectional study included 50 patients with diagnosed ILD over 24 months at a tertiary care center. All participants underwent spirometry and HRCT of the thorax. HRCT images were evaluated visually by an experienced radiologist and quantitatively using CALIPER-based LTA. Ground-glass opacity, reticulation, honeycombing, and fibrosis scores were correlated with spirometric parameters, particularly FVC% predicted, using Pearson correlation analysis. Results: Moderate, statistically significant positive correlations were observed between radiologist and CALIPER assessments for ground-glass opacity (r=0.634), reticulation (r=0.644), honeycombing (r=0.414), and fibrosis score (r=0.430). Fibrosis score showed a strong inverse correlation with FVC% predicted using CALIPER (r = −0.743, p<0.001) and a moderate inverse correlation using radiologist assessment (r = −0.493, p<0.001). Quantitative LTA showed good agreement with conventional visual HRCT assessment and reliably reflected functional impairment across different ILD subtypes. Conclusion: HRCT-derived fibrosis extent correlates significantly with pulmonary function impairment in ILD. CALIPER-based quantitative Lung Texture Analysis complements conventional HRCT interpretation by providing an objective and reproducible assessment of disease burden. Integration of quantitative imaging with spirometry may improve disease severity assessment, monitoring, and clinical decision-making in patients with ILD.