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

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.

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.

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).

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.