Baseline disease activity index and forced vital capacity predict clinically meaningful complications and mortality in systemic sclerosis.

Abstract

To evaluate whether the modified disease activity index (mDAI) predicts subsequent disease progression and organ damage in systemic sclerosis (SSc). We analyzed 227 patients diagnosed with SSc who were enrolled in a prospective SSc registry. Baseline disease activity was assessed using the mDAI; with active disease being defined as an mDAI ≥ 2.5. The primary outcome was a composite of disease-related clinically meaningful complications-based on revised CRISS step 1 events (interstitial lung disease progression, precapillary pulmonary hypertension, scleroderma renal crisis, heart failure, severe digital ischemia, or severe gastrointestinal dysfunction)-or all-cause mortality. Associations were examined using Cox proportional hazards models. At baseline, 42 (18.5%) had active disease. During a median follow-up period of 38 months, 45 (19.7%) patients had experienced the primary outcome. Active disease was associated with a higher risk of events (log-rank p < 0.001). In multivariable analysis, baseline active disease (HR 2.21, 95% CI 1.06-4.59) and a lower forced vital capacity (HR 0.98 per %, 95% CI 0.96-0.99) independently predicted adverse outcomes. Results were consistent across sensitivity analyses using alternative endpoint definitions. Baseline mDAI and forced vital capacity independently predict disease-related clinically meaningful complications and mortality in SSc. The mDAI provides a simple, feasible tool for risk stratification beyond progression of interstitial lung disease.