Next, to explore the diagnostic capabilities of serum calpain activity and HMGB1 levels for patients with SSc or SSc-ILD, we performed ROC that the AUC was 0.750 (p < 0.05) for serum calpain activity, 0.746 (p < 0.05) for HMGB1 levels, and 0.824 (p < 0.001) for the combination of them (Fig. 4a). Here, HMGB1 is linked to systemic sclerosis.