Sudoscan, a noninvasive tool for detecting diabetic small fiber neuropathy and autonomic dysfunction

Abstract

Objective: Sudomotor dysfunction may be an early detectable abnormality in diabetic small fiber neuropathy. The aim of this study was to evaluate the efficacy of Sudoscan™ (Impeto Medical, Paris, France) in detecting diabetic neuropathy (DN), in comparison with other standardized tests, in patients with diabetes mellitus (DM).

Subjects and methods: Sudoscan measures electrochemical skin conductance (ESC) of hands and feet through reverse iontophoresis. We evaluated 83 DM patients with and without DN and 210 healthy controls (HCs). Neuropathy Impairment Score-Lower Legs (NIS-LL), quantitative autonomic function testing (QAFT), and quantitative sensory testing (QST) were performed. Symptomatic pain was recorded using a visual analog scale. Receiver-operator characteristic (ROC) curves were calculated to evaluate the efficacy of Sudoscan in detecting DN compared with traditional modalities.

Results: Diabetes patients with DN had significantly worse ESCs of feet and hands than DM patients without DN and HCs (respectively, 56.3±3 vs. 75.9±5.5 and 84.4±0.9 [P<0.0001] for feet and 51.9±2.4 vs. 67.5±4.3 and 73.1±0.8 [P<0.0001] for hands). Increasing NIS-LL scores were associated with decreasing ESC values. ESCs correlated significantly with clinical (NIS-LL), somatic (QST), and autonomic (QAFT) measures of neuropathy and with pain scores. ROC curve analysis showed significant results for both hands and feet ESC (area under the curve of 0.86 and 0.88, respectively; P<0.0001) with sensitivity of 78% and specificity of 92% for feet to detect DN.

Conclusions: Sudoscan is a promising, sensitive tool to detect neuropathy in patients with DM. This is a very simple, easy-to-perform test that can be done in the clinical setting in 3-5 min.

Figures

FIG. 1.

Feet and hands electrochemical skin conductance (ESC) in healthy control (HC) subjects and diabetes mellitus (DM) patients with and without diabetic neuropathy. Data are mean±SEM values. *P<0.0001 versus HC and DM without neuropathy (by analysis of variance with post hoc analysis).

FIG. 2.

Motor, sensory, and total Neurologic Impairment Score—Lower Legs M-NISLL, S-NISLL, and T-NISLL, respectively; scores in patients with normal (≥60 μS) versus abnormal (P<0.0001 by analysis of variance.

FIG. 3.

Electrochemical skin conductance of (a) hands and (b) feet receiver-operator characteristic curve to reflect diabetic neuropathy. (a) Area under the curve=0.8563, P<0.0001. (b) Area under the curve=0.8755, P<0.0001.