Comparison of sudoscan and cardiovascular testing for assessment of cardiovascular autonomic neuropathy

Despite its frequency autonomic neuropathy is often poorly investigated. Cardiovascular Autonomic Neuropathy (CAN) has been shown to be one risk factor of morbi-mortality in some populations such as diabetic patients. Sympathetic C-fibers innervating sweat glands can be impaired early and measurement of sweat function has been suggested for early assessment of autonomic dysfunction. SUDOSCAN, a quick, non-invasive method to assess sudomotor function, based on an electrochemical reaction between sweat chloride and stainless-steel electrodes, was compared to usual methods for CAN investigation. 130 patients (mean age: 60.5 ± 13.2 y) addressed for autonomic assessment in various diseases (suspected small fiber neuropathy, parkinsonian syndromes,..) were investigated using Ewing tests and Heart Rate Variability (HRV). CAN severity was defined according to the “Ewing Score” (ES) based on HR variations during controlled breathing, stand test and Valsalva maneuver, BP variations during orthostatic and hand grip tests. LF (Low Frequency) and HF (High Frequency) power (HRV) considered to respectively reflect sympathetic and parasympathetic tone, were calculated in supine position and in a +75° tilt test. The SUDOSCAN device measures the Electrochemical Sweat Conductance (ESC) of the hands and feet in microSiemens (μS). A risk score for CAN is calculated from these conductances. For a cut-off value of 40μS for hand and foot ESC the OR for having mild dysautonomia or confirmed autonomic failure (Ewing score >1 vs others) were 14.0 [3.1-63.5] and 15.5 [1.9-123.0] respectively and for a cut-off value of 60 μS they were 2.5 [1.2-5.2] and 6.4 [2.4-17.0] respectively. These preliminary results suggest that SUDOSCAN allowing quick and quantitative assessment of sudomotor function may be an interesting tool for CAN detection. This has to be confirmed in a larger population.