Prognostic significance of 1-year pulmonary function changes in inflammatory myopathy-related interstitial lung disease

Abstract

BackgroundThe prognostic value of pulmonary function test (PFT) trends in idiopathic inflammatory myopathy-related interstitial lung disease (IIM-ILD) remains unclear. We evaluated whether one-year changes in forced vital capacity (FVC) and diffusing capacity (DLCO) predict 10-year mortality and lung transplantation.MethodsIn a retrospective, single-center cohort of adults with IIM-ILD classified by autoantibody status and 2017 EULAR/ACR criteria, ILD was defined by high-resolution chest CT (HRCT). Inclusion required baseline and follow-up PFTs 6–18 months apart. Cox regression and Kaplan-Meier analyses assessed associations between PFT changes and survival. Multivariable models adjusted for age, sex, smoking, baseline FVC, and PFT timing.ResultsThe most common IIM subset among 149 patients (mean age 50.5 ± 12.9 years, 63 % female) was anti-synthetase syndrome (73 %). Over mean 6.3-year follow-up, 41 (27.5 %) died and 6 (4.0 %) underwent transplantation. In multivariate analyses, absolute and relative FVC declines of ≥5% over one year were significantly associated with increased 10-year mortality (HR=2.78, CI 1.27–6.09, p = 0.01 and HR=2.37, CI 1.11–5.05, p = 0.025). Larger FVC declines (≥10%/≥15 %) showed stronger mortality associations, whereas stable or improved FVC predicted better outcomes (HR=0.38, CI 0.18–0.82, p = 0.01). DLCO decline was not associated with survival. Kaplan-Meier analysis demonstrated worse survival with FVC decline≥5 % (p = 0.028). Survival did not differ by autoantibody subtype or HRCT pattern.ConclusionEven modest FVC decline (≥5 %) over one year predicts mortality and transplant in IIM-ILD, while stabilization or improvement in FVC associates with improved survival and should be considered therapeutic goals. Routine FVC monitoring may support risk stratification, guide transplant referral, and serve as a trial endpoint.