Original articleA new simple method for assessing sudomotor function: Relevance in type 2 diabetesUne nouvelle méthode simple pour évaluer la function sudomotrice : intérêt dans le diabète de type 2
Introduction
Diabetes mellitus (DM) is one of the most common metabolic disorders in nearly all countries around the world. The global burden of DM in adults was estimated to be around 246 million in 2007 [1], and it is now also estimated that the global prevalence among adults will increase from 6.4% in 2010 to 7.7% by 2030 [2]. The diabetes epidemic is accelerating in the developing world, with an increasing proportion of affected individuals being in the younger age groups [2]. This is likely to increase the disease burden even further because of chronic diabetic complications such as neuropathy. Diabetic autonomic neuropathy (DAN) is a common multifactorial disease with a prevalence ranging from 7.7 to 90%, depending on the tests used, populations examined, and type and stage of disease [3]. Risk factors for the development of DAN include diabetes duration, age and long-term poor glycaemic control. Its major clinical manifestations include resting tachycardia, exercise intolerance, orthostatic hypotension, constipation, gastroparesis and sudomotor dysfunction. The clinical diagnostic signs are often silent or difficult to assess routinely, even in patients with peripheral neuropathy, and some studies suggest that small fibres may be injured early in the course of DM and particularly affect sudomotor function [4], [5]. As DM can remain asymptomatic for years, the screening, and thus, the diagnosis of neuropathy may be delayed, whereas its early detection could result in appropriate interventions, thereby reducing the incidence of complications such as diabetic foot [6].
Sudomotor function can be assessed through various tests. The quantitative sudomotor axon reflex test (QSART) is the most commonly used, as it is considered to be the most accurate and sensitive [7], [8]. This test measures sweat output in a reproducible and dynamic way (after simultaneous axon reflex stimulation), and relies on iontophoresis of quantified acetylcholine [7]. However, it also requires a high level of clinical expertise to perform and specialist facilities, and is too time-consuming for daily practice.
The aim of the present study of type 2 diabetic patients and healthy control subjects was to assess the sensitivity, specificity and reproducibility of EZSCAN, a new, noninvasive and quick method for the precise evaluation of sweat-gland function through electrochemical skin conductance (ESC) measurement.
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Study population
The present study included 133 type 2 diabetic patients (mean age: 58.9 ± 12.1 years; mean diabetes duration: 14 ± 10 years; 28% with nephropathy, 11% with retinopathy, 7% with peripheral neuropathy and 9% with cardiovascular complications; none using beta-blockers or angiotensin-converting enzyme [ACE] inhibitors) who had attended diabetes consultations at Bégin Hospital, and 41 healthy volunteers (mean age: 25.5 ± 6.4 years; no known risk of diabetes) living in Saumur. Approvals for the study
Results
The participants’ clinical characteristics, including FPG and HbA1c for the diabetic patients, are shown in Table 1. According to the patients’ selection, FPG was higher in the diabetics compared with the controls (9.7 ± 3.5 mmol/L vs 5.3 ± 0.8 mmol/L, respectively; P < 0.0001).
The ESC in both the hands and feet was significantly decreased in the diabetic patients (53 ± 16 μSi and 67 ± 14 μSi, respectively) compared with the healthy controls (68 ± 16 μSi and 80 ± 7 μSi, respectively; P < 0.0001) (Table 2). In
Discussion
The present study findings indicate that EZSCAN can detect sweat-gland dysfunction, a clinical manifestation of autonomic neuropathy in diabetic patients, which is consistent with the well-known observation that such patients have sudomotor dysfunction especially in the feet [15]. The sensitivity and specificity of this simple noninvasive method, as applied to a population of type 2 diabetic patients compared with healthy control subjects, were 75 and 100%, respectively.
This new method for
Conflict of interest statement
H.M., P.O.M. and B.B. have no potential conflicts of interest to disclose.
Funding: This work was funded by Impeto Medical, 17, rue campagne première, 75014 Paris, France.
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