Baseline characteristics of systemic sclerosis patients with restrictive lung disease in a multi-center US-based longitudinal registry.

Aim: Interstitial lung disease (ILD) is the leading cause of disease-related death in systemic sclerosis (SSc). Here, we assess baseline characteristics of SSc subjects with and without restrictive lung disease (RLD) in a multi-center, US-based registry.

Methods: SSc patients within 5 years of disease onset were enrolled in the Collaborative National Quality and Efficacy Registry (CONQUER), a multi-center US-based registry of SSc study participants (age ≥ 18 years) enrolled at 13 expert centers. All subjects met 2013 American College of Rheumatology / European League Against Rheumatism criteria. Subjects with a pulmonary function test (PFT) at baseline before April 1, 2020 were included. High-resolution computed tomography scan of the chest was not available to characterize ILD for all subjects. RLD was defined as forced vital capacity (FVC) <80% or total lung capacity (TLC) <80% predicted.

Results: There were 160 (45%) SSc subjects characterized as having RLD. There was no significant difference in age, gender or disease duration. RLD subjects had a mean disease duration from date of first non-Raynaud's symptom of 2.6 years and a mean FVC% predicted of 67% at baseline. In multivariable analysis, non-White race, higher physician global health assessment and modified Medical Research Council (mMRC) dyspnea scores, were independently associated with RLD. In the subgroup of RLD subjects with ILD, ILD had a negative correlation with RNA polymerase III antibody.

Conclusion: CONQUER is the largest, multi-center, prospective cohort of early SSc patients in the US. Non-White race was independently associated with RLD. In addition, 45% of CONQUER subjects already had RLD, highlighting the importance of screening for SSc-ILD at initial diagnosis.