Rheumatoid Arthritis-Associated Interstitial Lung Disease: Clinical Characteristics and Predictors of Mortality

INTRODUCTION: Interstitial lung disease (ILD) is a serious extraarticular manifestation of rheumatoid arthritis (RA), but no evidence-based therapy exists. Ongoing studies investigate the role of antifibrotic therapies for progressive fibrosing ILD (PF-ILD), including RA-ILD. The aim of the present study was to investigate the frequency of PF-ILD and the clinical characteristics of RA-ILD in a well-characterised, population-based cohort. METHODS: We identified patients with RA-ILD diagnosed and followed at the ILD referral centre in Aarhus, Denmark, from 2004 to 2016. Adjusted hazard rate ratios for death were estimated using Cox regression models. The presence of PF-ILD was assessed using recently proposed definitions of relative forced vital capacity (FVC) decline ≥10%, relative diffusion capacity of the lung for carbon monoxide (DLco) decline ≥15% or worsening symptoms or a worsening radiological appearance accompanied by a ≥5 to <10% FVC decline. RESULTS: We identified 102 patients with RA-ILD, and 52% had PF-ILD. Mean follow-up was 3.8 years and median survival was 7.1 years. Thirty-eight patients died during follow-up, and most deaths were from respiratory causes. Predictors of mortality in a multivariate model were DLco and high titres of IgM rheumatoid factor. CONCLUSION: PF RA-ILD was common and the associated mortality was high.