Systemic Sclerosis-Associated ILD: Insights and Limitations of ScleroID

Background: Pulmonary involvement in systemic sclerosis (SSc) is typically assessed using pulmonary function tests (PFTs), high-resolution CT (HRCT), and composite indices. Patient-reported outcomes (PRO), including ScleroID, provide insight into quality of life, but their relationship with clinical measures and role in overall disease assessment remain unclear. Objective: To assess the correlation between ScleroID scores and both lung involvement and disease activity/damage in a cohort of SSc-ILD patients from a large tertiary care center. Methods: Disease activity [European Scleroderma Study Group Activity Index (EScSG-AI), Scleroderma Clinical Trials Consortium Activity Index (SCTC-AI)], disease severity [Medsger severity scale (MSS)], and PRO measure ScleroID were assessed for associations with the extent and severity of SSc-ILD. Results: : Eighty-two SSc patients (mean age 56.0 ± 10.8 years; median disease duration 4.2 ± 4.7 years) were included. Baseline lung function was moderately impaired (FVC 76.8%, DLCO 54.3%), with mean ESsSG-AI 6.1 ± 1.7, SCTC-AI 34.5 ± 14.8, Medsger severity 9.6 ± 3.8, and ScleroID total 4.1 ± 2.4. Diffuse cutaneous SSc, ATA positivity, NYHA class > III dyspnea, FVC < 80% predicted, HRCT fibrosis >20%, and pulmonary hypertension were associated with higher disease activity and severity scores. Patients with ≥20% fibrosis reported worse ScleroID scores for fatigue, social life, mobility, and breathlessness compared with those with 10–20% fibrosis (p = 0.001–0.02). Higher ScleroID scores correlated with lower FVC%, shorter 6-MWD, and greater ILD extent on HRCT. ScleroID domains were strongly interrelated in both fibrosis subgroups. In patients with >20% fibrosis, fatigue, mobility, and social impact correlated with clinical activity and severity scores (r = 0.373–0.635, all p < 0.05), while correlations were weak or absent in the 10–20% group. Breathlessness showed minimal associations in both subgroups. Overall, ScleroID captured patient-perceived disease burden—including fatigue, mobility, and social limitations—more closely reflecting functional impact than objective measures in patients with less extensive fibrosis. Conclusions: SSc-ILD patients experience a higher disease burden, with breathlessness as a key feature. ScleroID captured disease impact mainly in those with advanced fibrosis (≥20% lung involvement), suggesting it may underestimate impact in patients with milder ILD.