Interstitial lung disease in anti-U1RNP systemic sclerosis patients: A European Scleroderma Trials and Research analysis

BACKGROUND: Interstitial lung disease is the leading cause of morbidity and mortality in systemic sclerosis, but it is characterized by significant heterogeneity in patient outcomes. So far, little is known about the influence of anti-U1RNP antibodies on lung outcomes in systemic sclerosis-associated interstitial lung disease patients. METHODS: European Scleroderma Trials and Research group systemic sclerosis patients with radiological-confirmed interstitial lung disease, available %predicted forced vital capacity, and autoantibody status were included. Baseline demographic and disease features were compared between anti-U1RNP positive and anti-U1RNP negative patients. Moreover, longitudinal analyses were done measuring relative change in %predicted forced vital capacity over 12 ± 6, 24 ± 6, and 36 ± 6 months, and changes were classified into stable (⩽ 4%), mild (5%-9%), and major progression (⩾ 10%). Predictors associated with death of any cause or major interstitial lung disease progression were evaluated in systemic sclerosis-associated interstitial lung disease patients with or without anti-U1RNP antibodies. Logistic regression analyses and Cox proportional hazards models adjusted for age and FVC were applied. RESULTS: A total of 6043 systemic sclerosis-associated interstitial lung disease patients were included for the analysis, among which 327 (5.4%) were positive for anti-U1RNP antibodies. Mean age was 56.8 ± 13.2 years and 4971 (82.3%) were women. Anti-U1RNP + systemic sclerosis-associated interstitial lung disease patients had more frequently limited cutaneous systemic sclerosis (63.5.5% vs 53.3%, p < 0.001), higher frequency of joint synovitis (18.1% vs 13.9%, p = 0.039), and myositis (24.0% vs 19.5%, p = 0.048). Anti-U1RNP + patients had a baseline lower mean forced vital capacity (82.0% vs 86.0%, p < 0.001) and lower mean %predicted diffusing capacity for carbon monoxide (57.0% vs 60.5%, p = 0.003). Periods of mild or major FVC decline and mortality rates were not statistically different between the groups. CONCLUSION: Systemic sclerosis-associated interstitial lung disease patients positive for anti-U1RNP antibodies have more impaired baseline lung function but similar trajectories of forced vital capacity changes and mortality during the first 3 years of follow-up.