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

OBJECTIVE: To evaluate whether the modified disease activity index (mDAI) predicts subsequent disease progression and organ damage in systemic sclerosis (SSc). METHODS: 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. RESULTS: 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. CONCLUSION: 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.