Meaningful thresholds for change in quantitative computed tomography–derived fibrosis extent in idiopathic pulmonary fibrosis

Abstract Rationale Validated thresholds for clinically meaningful change in quantitative computed tomography (QCT) for fibrosis extent across algorithms remain unclear in idiopathic pulmonary fibrosis (IPF). Objectives To evaluate minimal clinically important difference (MCID) for 1-year change in QCT metrics in IPF using different algorithms than previously reported and to identify prognostically meaningful thresholds for effective risk stratification. Methods This multicenter retrospective study included IPF patients with baseline and 1-year follow-up CT. Minimal clinically important differences for change in fibrosis score (ΔFS) derived from fully automated CT quantification were estimated using an anchor-based approach with 1-year changes in FVC and diffusing capacity for carbon monoxide (DLco), and a prognostic threshold was estimated using maximally selected log-rank statistics. Prognostic significance of ΔFS was evaluated in discovery and validation cohorts. Results The discovery cohort included 524 patients (mean age = 66.8 years; 79% men), and the external validation cohort included 224 patients (mean age = 69.6 years; 83% men). Anchor-based MCIDs were 2.72% for FVC and 4.52% for DLco, with a prognostic threshold of 4.05%. In the discovery cohort, 1-year ΔFS were independently associated with transplant-free survival (TFS), with greater risk when ΔFS exceeded MCID or prognostic thresholds (all, P  Conclusion One-year change in FS and its thresholds were significantly associated with TFS, supporting annual CT follow-up with predefined QCT thresholds for monitoring and risk stratification in IPF.