Comparison of the disease activity score and the revised EUSTAR activity index in diffuse cutaneous systemic sclerosis patients.

OBJECTIVES: To compare the ability of the Disease Activity Score (DAS) and the Revised EUSTAR Activity Index (RAI) to detect diffuse cutaneous systemic sclerosis (dcSSc) patients requiring treatment intensification in a Belgian cohort. METHODS: We retrospectively compared the widely used DAS and the recently developed RAI in a longitudinal cohort (median follow-up of 42 months) of 62 dcSSc patients, of whom 30 with a disease duration ≤3 years at inclusion. Active disease was defined by a DAS ≥3/10 or a RAI ≥2.5/10. We chose a pragmatic definition to assess disease progression, namely any start or increase of glucocorticoids, immunosuppressants, anti-endothelin receptors or prostanoids. Sensitivity, specificity, negative and positive predictive values (NPV and PPV) of DAS and RAI for prediction of actual treatment changes were compared by ROC curves. RESULTS: According to RAI, 48% (of all dcSSc patients) and 55% (of ≤3 years dcSSc patients) were categorised as effectively active during follow-up while 34% and 43% according to DAS, respectively. The PPV and the NPV to detect disease progression, in ≤3 years dcSSc patients, were 59% and 89% for RAI vs 73% and 87% for DAS, respectively. The area under ROC curves were high for both scores (0.85 for RAI and 0.87 for DAS). CONCLUSIONS: Both scores are proven as predictive to detect disease activity, with a slightly better sensitivity for RAI. By contrast, RAI lacks specificity in predicting a real need for treatment intensification, thereby possibly leading to overtreatment.