Tracking Impact of Interstitial Lung Disease in Systemic Sclerosis in a Complete Nationwide Cohort

Rationale: Interstitial lung disease (ILD) represents a major challenge in systemic sclerosis (SSc), but there are no precise, population-based data on its overall impact, limiting opportunities for screening and management strategies. Objectives: Evaluate impact of ILD in a unique, nationwide, population-based SSc cohort. Methods: ILD was assessed prospectively in the Norwegian SSc (Nor-SSc) cohort, including all 815 patients with SSc resident in the country from 2000 to 2012. Lung high-resolution computed tomography (HRCT) scans were available for fibrosis quantification at baseline (n = 650, 80%) and follow-up. Pulmonary function tests were assessed at baseline (n = 703, 86%) and follow-up. Vital status and standardized mortality ratios (SMRs) were estimated at study end (2018) in the 630 incident Nor-SSc cases and 15 individually matched control subjects. Cumulative survival rates were computed. Measurements and Main Results: At baseline, 50% of the subjects with SSc (n = 324) had ILD by HRCT and 46% displayed pulmonary function declines consistent with ILD progression. Mortality correlated with extent of lung fibrosis as SMR increased from 2.2 with no fibrosis to 8.0 with greater than 25% fibrosis. SMR was inversely related to baseline FVC% and increased at all FVC levels below 100%. In patients with normal-range baseline FVC (80-100%), the 5- and 10-year survival rates correlated with presence or absence of lung fibrosis, being 83% and 80%, respectively, with no fibrosis and 69% and 56%, respectively, with lung fibrosis (P = 0.03). Conclusions: The mere presence of ILD at baseline appears to affect outcome in SSc, suggesting that all patients with SSc should undergo a baseline pulmonary function test and lung HRCT screening to diagnose ILD early and tailor further management.