Sudoscan® and QSART in the composite autonomic severity scale: complementary approaches to sudomotor assessment in multiple sclerosis.

INTRODUCTION: The Quantitative Sudomotor Axon Reflex Test (QSART) is the gold standard for evaluating sudomotor function in the Composite Autonomic Scoring Scale (CASS). Sudoscan® has been proposed as a potential alternative. This study investigated whether Sudoscan®-derived indices could replace QSART within the CASS framework and provide reliable sudomotor evaluation in people with multiple sclerosis (pwMS). METHODS: This study included 99 pwMS. Subjective autonomic symptoms were assessed with the Composite Autonomic Symptom Score-31 (COMPASS-31), and objective autonomic testing was performed with the CASS, which includes QSART for sudomotor assessment. Additionally, all pwMS underwent Sudoscan® testing, and a modified CASS score was derived from adrenergic, cardiovagal, and Sudoscan®-based sudomotor measures. RESULTS: A strong correlation was observed between CASS and modified CASS (r = 0.795, p < 0.001). Autonomic dysfunction (CASS ≥ 1) was present in 72.7% of participants, while 77.7% had modified CASS ≥ 1. However, no correlation was found between QSART- and Sudoscan®-based sudomotor indices (r = 0.043, p = 0.672).CASS did not correlate with COMPASS-31 or its subdomains, whereas modified CASS correlated with the gastrointestinal domain of COMPASS-31 (r = 0.228, p = 0.027). Additionally, modified CASS correlated with age (r = 0.204, p = 0.048) and the Expanded Disability Status Scale (EDSS) score (r = 0.207, p = 0.043). CONCLUSIONS: The modified CASS, including Sudoscan® sudomotor testing, showed a strong overall correlation with the standard CASS and meaningful associations with age and disability level. More long-term studies are needed to assess its effectiveness in monitoring sudomotor dysfunction over time.