Abstract Rationale Forced vital capacity (FVC) decline has been associated with increased mortality and reduced quality of life among interstitial lung disease (ILD) patients. However, there remains limited data on the ability of FVC decline to predict further physiological progression in fibrotic ILD. We assessed the relationship of FVC trajectory at 6 months on transplant free survival (TFS) and subsequent FVC progression among patients enrolled in the Australasian ILD Registry (AILDR), a prospective, bi-national registry. Methods All AILDR participants with at least two serial lung function and follow-up for at least one-year post-ILD diagnosis were included. Relative lung function change at 6 months was determined using a mixed effect model with random intercept for identifier and random slope for year, adjusted for age, gender, baseline FVC and diagnosis. The association with FVC change at 6 months and subsequent FVC change over time was evaluated. Cox proportional hazards models were used to assess association with TFS. Results were stratified by idiopathic pulmonary fibrosis (IPF) and non-IPF groups. Results 4503 participants were included: 56.0% male, median age 68.5 (58.8;76.3) years, 1171(26.0%) with IPF and 3332 (74.0%) with non-IPF, and 1233 (27.4%) receiving anti-fibrotic medications; baseline mean FVC 86.1% (70.9;100.0) and DLCO 66.9% (52.4;82.0). Over the 10 year follow-up, 1013 (32.0%) died and 101 (3.2%) were transplanted. Greater relative percent predicted (pp) FVC decline over the first 6 months was associated with worse TFS in IPF (HR 8.26, 95% CI, 4.80, 14.22) and non-IPF patients (HR 2.31, 95% CI 1.95, 2.72). Relative ppFVC change in the first 6 months significantly modified subsequent FVC trajectory (p 0.001). In IPF, each increment of 1% relative change was associated with a 0.8% (95%CI 0.7, 0.8) greater change in ppFVC per year; in non-IPF, each increment was associated with a 1.0% (95%CI 0.9, 1.0) greater change in ppFVC per year. Among IPF participants, a 5% relative ppFVC decline at 6 months was associated with mean -8.8% (95%CI, -10.5, -7.0%) and -22.6% (95%CI, -25.1, -20.1%) ppFVC fall over 1 and 3 years respectively. In non-IPF participants, a 5% relative ppFVC decline was associated with -5.2% (95%CI, -5.9, -4.5%) and -18.4% (95%CI, -20.5, -18.2%) mean ppFVC fall at 1 and 3 years. Conclusion A 5% relative FVC decline at six months is associated with reduced TFS and further ppFVC decline in fibrotic ILD patients. This abstract is funded by: Boehringer Ingelheim
Li et al. (2026) studied this question.