LAUSR

Background Interstitial lung disease (ILD) is a serious extraarticular manifestation of rheumatoid arthritis (RA) associated with excess mortality. No evidence-based approach to therapy for RA-ILD exists, but ongoing studies investigate the role of antifibrotic therapies for progressive fibrosing ILD, including progressive fibrosing RA-ILD. Objectives The aim of the present study was to investigate the frequency of progressive fibrosing ILD, the clinical characteristics and mortality of RA-ILD in a well-characterised, population-based cohort. Methods We identified patients with RA-ILD diagnosed and followed at the ILD referral center in Aarhus, Denmark between 2004 and 2016. Adjusted hazard rate ratios for death were estimated using Cox regression models. The presence of progressive fibrosing 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-<10% relative decrease in FVC. Results We identified 102 patients with RA-ILD. Mean follow-up was 3.8 years and median survival was 7.1 years. Thirty-eight patients died during follow-up, and the majority of deaths were from respiratory causes. Predictors of mortality in a multivariate model were DLco and high titers of IgM rheumatoid factor, but not the presence of a UIP-pattern on high resolution computed tomography. Fifty-three patients (52%) had progressive fibrosing ILD. Progressive fibrosing RA-ILD n=53 Stable RA-ILD n=49 p-value Typical UIP n=42 Probable UIP n=13 NSIP n=43 p-value** Age (SD) 68.8 (9.6) 67.6 (11.7) 0.86 70.2 (9.7) 69.2 (7.3) 66.2 (12.1) 0.17 Female gender% 51 57 0.53 50 54 53 0.80 FVC (SD) 87.3 (24.7) 91.7 (24.2) 0.35 86.5 (25.1) 91.8 (30.6) 92.2 (21.7) 0.39 DLco 53.9 (17.9) 55.8 (14.6) 0.57 52.7 (15.9) 55.4 (21.7) 55.7 (14.5) 0.49 High titer of IgM RF n%* 36 (68) 28 (57) 0.16 33(79) 9 (69) 22 (51) 0.013* *>3 x upper limit of normal ** typical and probable UIP vs NSIP Clinical characteristics for progressive fibrosing RA-ILD and stable RA-ILD at the time of the ILD diagnosis and stratified by HRCT pattern. Conclusion Progressive fibrosing RA-ILD was common and the associated mortality was high. IgM rheumatoid factor and DLco were independent predictors of mortality. Acknowledgement None Disclosure of Interests None declared