Detection of neuropathy using a sudomotor test in type 2 diabetes

Abstract

Background

The sudomotor test is used to evaluate the postganglionic cholinergic sympathetic nervous system. The aim of this study was to evaluate the efficacy of a sudomotor testing device to detect peripheral distal neuropathy (PDN) and cardiac autonomic neuropathy (CAN) in patients with type 2 diabetes.

Materials and methods

A total of 133 type 2 diabetic patients were included in the study. The patients underwent examination at the IPC Heart Care Centre (Mumbai, India) in order to assess the diabetic neuropathy symptoms (DNS) score, using a questionnaire, and the CAN score, using heart rate variability analysis and Ewing tests. In addition, patients were given a sudomotor test using the SudoPath™ system. The diagnosis of PDN is based on the DNS score. A DNS score of 1 or higher is defined as a positive result for PDN. According to the DNS score, the patients were separated into two groups: Group 1 comprised 35 patients (21 males), with the mean age of 66 years (standard deviation [SD] =12.1), who had a DNS score ≥1. Group 2 comprised 98 patients (65 males), with the mean age of 56 years (SD =9.6), who had a DNS score =0. The SudoPath system is a galvanic skin response device that uses the quantitative sudomotor axon reflex approach to assess for small and unmyelinated fiber neuropathy. The system provides a sudomotor response (SMR) score based on these three measured sudomotor parameters. A statistical analysis was performed using the analysis of variance to compare mean differences between the groups as well as receiver operating characteristic (ROC) curves, to determine the specificity and sensitivity of SMR score to detect PDN, comparing the diabetic groups 1 and 2, and the coefficient of correlation between the CAN score and the SMR score in all the subjects included in the study.

Results

When comparing the diabetes groups 1 and 2, the SMR Score had a sensitivity of 91.4% and specificity of 79.1% (cutoff number >3) to detect PDN ( P=0.0001). Area under the ROC curve (AUC) =0.893. A correlation analysis of the CAN score and SMR score returned a coefficient of correlation r=0.68 ( P<0.0001).

Conclusion

The SudoPath system is easy to use, operator-independent, and fast (3-minute testing time). This study shows that the device will be useful to assess the susceptibility of type 2 diabetes patients in developing PDN complications.