Elsevier

Diabetes & Metabolism

Volume 37, Issue 6, December 2011, Pages 527-532
Diabetes & Metabolism

Original article
Non-invasive and quantitative assessment of sudomotor function for peripheral diabetic neuropathy evaluationMesure non invasive et quantitative de la fonction sudorale pour mieux évaluer la neuropathie périphérique chez le patient

https://doi.org/10.1016/j.diabet.2011.05.003Get rights and content

Abstract

Aims

Perturbation of pain sensation is considered one of the major initiating risk factors for diabetic foot ulcer. Sweat dysfunction leading to abnormal skin conditions, including dryness and fissures, can increase foot ulcer risk. The aim of this study was to evaluate Sudoscan™, a new, quick, non-invasive and quantitative method of measuring sudomotor dysfunction as a co-indicator of the severity of diabetic polyneuropathy (DPN).

Methods

A total of 142 diabetic patients (age 62 ± 18 years, diabetes duration 13 ± 14 years, HbA1c 8.9 ± 2.5%) were measured for vibration perception threshold (VPT), using a biothesiometer, and for sudomotor dysfunction, using electrochemical sweat conductance (ESC) based on the electrochemical reaction between sweat chloride and electrodes in contact with the hands and feet. Retinopathy status was also assessed, as well as reproducibility between two ESC measurements and the effect of glycaemia levels.

Results

ESC measurements in the feet of patients showed a descending trend from 66 ± 17 μS to 43 ± 39 μS, corresponding to an ascending trend in VPT threshold from < 15 V to > 25 V (P = 0.001). Correlation between VPT and ESC was −0.45 (P < 0.0001). Foot ESC was lower in patients with fissures, while VPT was comparable. Both VPT and foot ESC correlated with retinopathy status. Bland–Altman plots indicated good reproducibility between two measurements, and between low and high glycaemia levels.

Conclusion

Sudoscan™ is a reproducible technique with results that are not influenced by blood glucose levels. Sweating status may be a quantitative indicator of the severity of polyneuropathy that may be useful for the early prevention of foot skin lesions.

Résumé

Introduction

La perte de sensibilité est considérée comme le facteur de risque majeur « du pied diabétique ». La perturbation de la fonction sudorale favorisant la survenue d’anomalies cutanées (sécheresse de la peau et fissures) peut également augmenter le risque. Le but de cette étude était d’évaluer une nouvelle méthode rapide, non-invasive, et quantitative (Sudoscan™) destinée à mesurer la fonction sudorale comme co-indicateur de la sévérité d’une neuropathie périphérique diabétique.

Patients et méthodes

Cent quarante-deux patients diabétiques (âge 62 ± 18 ans, ancienneté du diabète 13 ± 14 ans, HbA1c 8,9 ± 2,5 %) ont bénéficié d’une mesure du seuil de perception vibratoire avec un biothésiomètre et de la fonction sudorale par mesure au niveau des pieds de la conductance électrochimique résultant de la réaction entre les chlorures de la sueur et des électrodes en contact avec les pieds et les mains. L’atteinte rétinienne a été également déterminée. La reproductibilité entre deux mesures et l’effet du niveau glycémique sur les mesures ont également été évalués.

Résultats

La conductance des pieds passe de 66 ± 17 μS à 43 ± 39 μS quand le seuil de perception vibratoire passe de < 15 V à > 25 V (P = 0,001) avec une corrélation de −0,45 (P < 0,0001) entre ces deux paramètres. Chez les patients ayant des fissures, la conductance des pieds est abaissée alors que le seuil de perception vibratoire n’est pas encore discriminant. Ces deux paramètres sont corrélés aux lésions observées au fond d’œil. Un graphe de Bland-Altman indique une bonne reproductibilité pour les conductances électrochimiques des pieds entre deux mesures et entre des mesures à un niveau haut ou normal de la glycémie.

Conclusion

Le Sudoscan™ est une méthode reproductible et les résultats ne sont pas influencés par la glycémie. L’évaluation de la fonction sudorale peut constituer un indicateur quantitatif de la sévérité d’une polyneuropathie utile dans la prévention du pied diabétique.

Introduction

Diabetic polyneuropathy (DPN) is a nerve-length-dependent process [1]. Early detection of symmetrical distal sensory–motor DPN can decrease morbidity and the risk of foot complications [2]. Sensory function is considered one of the major initiating risk factors in the pathogenesis of diabetic foot ulcer [3]. As no gold standard is available for early diagnosis of DPN, vibration perception threshold (VPT), using a biothesiometer, and pressure perception, using Semmes–Weinstein monofilaments, have been proposed to identify patients at risk, but none of these investigates peripheral autonomic involvement [4].

Peripheral autonomic neuropathy (PAN) results in the atrophy of sweat glands and decreased sudomotor response that may affect the skin suppleness and flexibility that prevent skin cracks and ulceration, and may also reduce sweating, leading to abnormal skin conditions such as dryness, fissures and blisters [5], [6]. The prevalence of PAN, as determined by the presence of two or more clinical signs, has recently been estimated to affect 43% of diabetic patients aged 40–70 years [7], [8]. PAN is usually evaluated through sweat function, using the sympathetic skin response (SSR), or by quantitative sudomotor axon reflex testing (QSART) [9]. These methods require specialized training to perform and are also time-consuming procedures. Neuropad® is another alternative test targeted for use by the patient, although it is less sensitive and semi-quantitative [10].

Sudoscan™, a new non-invasive and rapid technique, has recently been developed to allow the precise quantitative evaluation of sweat gland function through measurement of electrochemical sweat conductance (ESC) on the hands and feet based on sweat chloride concentrations [11]. The aim of the present study was to analyze in diabetic patients the relationship between VPT and foot ESC, the reproducibility and effect of blood glucose levels on ESC measurements, and the relationship between ESC results and foot fissure presence.

Section snippets

Participants and study protocol

Altogether, 142 consecutive patients were recruited from the diabetes clinic at Haut-Lévêque University Hospital after their informed consent was obtained. Patients were accepted on the condition of having had a diagnosis of diabetes with different degrees of peripheral nerve involvement, but no progressive skin lesion that might induce foot ulceration. They were divided according to peripheral somatic neuropathy, as assessed by their VPT value as a reference (consecutive patients to obtain the

Results

Of our 142 diabetic patients, 55 had a VPT threshold less than 15 V, 30 had a threshold between 15–25 V and 57 had a threshold greater than 25 V. Their main characteristics by VPT are presented in Table 1. Patients were older and had longer diabetes durations as VPT increased from less than 15 V to greater than 25 V, whereas no statistical difference was found among the different diabetic groups in mean HbA1c.

Also, among our study patients, 66 had no sudomotor dysfunction (foot ESC > 60 μS), 43 had

Discussion

This study shows that the assessment of sudomotor function based on sweat chloride concentration through reverse iontophoresis is a quantitative reproducible method that is not influenced by glycaemia. Foot ESC correlates with different degrees of peripheral sensory neuropathy, as estimated by VPT measurement and monofilament tests, and there is also progressive worsening of ESC measurements with increasing VPT and monofilament results. Moreover, sudomotor dysfunction as assessed by ESC results

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

Acknowledgments

We would like to thank P. Brunswick, X. Neveu and J.H. Calvet for their technical assistance, analysis of data and contribution to discussions.

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