SUDOSCAN: A Simple, Rapid, and Objective Method with Potential for Screening for Diabetic Peripheral Neuropathy

Abstract

Clinical methods of detecting diabetic peripheral neuropathy (DPN) are not objective and reproducible. We therefore evaluated if SUDOSCAN, a new method developed to provide a quick, non-invasive and quantitative assessment of sudomotor function can reliably screen for DPN. 70 subjects (45 with type 1 diabetes and 25 healthy volunteers [HV]) underwent detailed assessments including clinical, neurophysiological and 5 standard cardiovascular reflex tests (CARTs). Using the American Academy of Neurology criteria subjects were classified into DPN and No-DPN groups. Based on CARTs subjects were also divided into CAN, subclinical-CAN and no-CAN. Sudomotor function was assessed with measurement of hand and foot Electrochemical Skin Conductance (ESC) and calculation of the CAN risk score. Foot ESC (μS) was significantly lower in subjects with DPN [n = 24; 53.5(25.1)] compared to the No-DPN [77.0(7.9)] and HV [77.1(14.3)] groups (ANCOVA p<0.001). Sensitivity and specificity of foot ESC for classifying DPN were 87.5% and 76.2%, respectively. The area under the ROC curve (AUC) was 0.85. Subjects with CAN had significantly lower foot [55.0(28.2)] and hand [53.5(19.6)] ESC compared to No-CAN [foot ESC, 72.1(12.2); hand ESC 64.9(14.4)] and HV groups (ANCOVA p<0.001 and 0.001, respectively). ROC analysis of CAN risk score to correctly classify CAN revealed a sensitivity of 65.0% and specificity of 80.0%. AUC was 0.75. Both foot and hand ESC demonstrated strong correlation with individual parameters and composite scores of nerve conduction and CAN. SUDOSCAN, a non-invasive and quick test, could be used as an objective screening test for DPN in busy diabetic clinics, insuring adherence to current recommendation of annual assessments for all diabetic patients that remains unfulfilled.

Fig 1. SUDOSCAN.

Fig 2. Box and whisker plots of SUDOSCAN outcomes of each study group. A, Foot Electrochemical Skin Conductance (FESC, μS) in healthy volunteers and subjects with type 1 diabetes divided into subjects with no diabetic peripheral neuropathy (No DPN) and DPN; B, Hand Electrochemical Skin Conductance (HESC, μS) in HV, No DPN and DPN groups; C, FESC in HV and subjects with type 1 diabetes divided into subjects with no Cardiac Autonomic Neuropathy (No CAN) and CAN; D, HESC in HV, No CAN and CAN groups.

Fig 3. Graphic presentation of the diagnostic performance of (A) Foot Electrochemical Skin Conductance (FESC, μS) and (B) Cardiac Autonomic Neuropathy Risk Score (CAN-RS) by Receiver Operating Curve (ROC) analysis for diabetic peripheral neuropathy (A) and cardiac autonomic neuropathy (B, CAN).