Assessment of fibrosing interstitial lung disease progression: CT visual score on radiological progressive pulmonary fibrosis criteria versus 3D-CT volume-histogram analysis

PURPOSE: To identify the most reproducible visual scoring approach on radiological criteria of the 2022 progressive pulmonary fibrosis (PPF) guideline and compare its association with pulmonary function test (PFT) decline against quantitative 3D-CT volume-histogram analysis (VHA) metrics in fibrosing interstitial lung disease (ILD). MATERIALS AND METHODS: In this single-center retrospective study, 92 patients with fibrosing ILD underwent paired thin-section CT and PFTs at a median 44.5-month interval. Five guideline-defined CT features were visually scored as a percentage of lung involvement on five axial sections at baseline and follow-up; the sum of changes in each feature constituted the total visual score change (ΔCT-score). Interobserver reliability was assessed using intraclass correlation coefficients (ICC). Quantitative metrics included changes in skewness, kurtosis, and entropy derived from VHA, and total-lung volume change (ΔV-LUNG) through volumetric analysis. Associations with changes in percent-predicted forced vital capacity (%FVC) and diffusing capacity for carbon monoxide (%DLCO) were evaluated using Spearman correlation coefficients. Discriminatory performance for disease progression was assessed using receiver operating characteristics. RESULTS: ΔCT-score demonstrated excellent interobserver reliability (ICC, 0.94-0.96) and strong correlations with VHA metrics (Spearman r: Δskewness, - 0.78; Δkurtosis, - 0.74; Δentropy, 0.73). VHA metrics correlated substantially with Δ%FVC (r: Δskewness, 0.64; Δkurtosis, 0.61; Δentropy, - 0.61), comparable to ΔCT-score (r, - 0.60), whereas correlations with Δ%DLCO were moderate (r: Δskewness, 0.58; Δkurtosis, 0.55; Δentropy, - 0.58; ΔCT-score, - 0.48). ΔV-LUNG correlated with Δ%FVC (r, 0.61) and Δ%DLCO (r, 0.51). All correlations were statistically significant (p < 0.001). All metrics showed good discriminatory performance for radiological and/or physiological evidence of disease progression by PPF guideline definition, with area-under-the-curve values of 0.76-0.89. CONCLUSION: VHA metrics demonstrated utility comparable to reproducible visual scoring for identifying radiological progression and physiological decline in fibrosing ILD. Automated VHA can offer an objective, reproducible alternative to laborious visual assessment for disease progression in fibrosing ILD.