Background Endpoints in systemic sclerosis (SSc), such as modified Rodnan skin score (mRSS) and pulmonary function tests represent only parts of a multisystem disease. The European Scleroderma Study Group (EScSG) developed an SSc activity index, which captures involvement of multiple organs. The predictive validity of the SSc activity index is unclear.
Objectives To estimate the effect of disease activity as measured by EScSG activity index, on the risk of subsequent organ damage in the Canadian Scleroderma Research Group (CSRG) cohort.
Methods Of 421 SSc patients from the CSRG database with disease duration of ≤3 years, 197 who had no evidence of endstage organ damage initially and 3-year follow-up were included. Disease activity was assessed by EScSG activity index with two variability measures: 1. adjusted mean (am) EScSG activity score (the area under the curve of EScSG activity index over observation period), and 2. persistently active disease (PAD)/flare (EScSG score of ≥3 at follow-up visit). Internal organ involvement assessed over follow-up was based on Medsger severity scale and included accrual of a new severity score overall and by specific organ systems. Adjusted odds ratios (OR) for association between disease activity, severity and progression were calculated using regression analysis.
Results After adjustment for covariates, amEScSG activity score was the most consistent predictor of risk at 3 year follow-up: disease progression as accrual of a new severity grade (Δ≥1) in any of the major internal organs (OR 1.42, 95%CI 1.14–2.25, p=0.007), lung disease (OR 1.86, 95%CI 1.31–2.64, p<0.0001), decline in FVC (OR 3.05, 95%CI 1.47–6.31, p=0.003) and DLCO (OR 1.61, 95%CI 1.06–2.46, p=0.026), ΔHAQ (OR 1.729, 95%CI 1.250–2.391, p<0.001), severity of visceral disease (Table). amEScSG predicted accrual of organ damage only in diffuse cutaneous SSc (dcSSc). In the multivariable analysis, progression of lung disease in dcSSc was predicted by amEScSG activity score (p=0.006), and severity of lung disease by amEScSG (p<0.0001), older age (p=0.023), mRSS (p<0.001) and initial severity of lung disease (p<0.0001). The best predictor of renal disease severity at 3-year was initial severity of kidney involvement (p<0.0001).
Conclusions The mean adjusted EScSG reliably captured disease activity over time in individual patients and predicted the risk of deterioration in health status, disease progression and development of severe internal organ involvement in diffuse SSc, after adjustment for key covariates.
Disclosure of Interest None declared