Feasibility and Effectiveness of Electrochemical Dermal Conductance Measurement for the Screening of Diabetic Neuropathy in Primary Care.

The prevalence of diabetes mellitus (DM) is very high in Spain, being nearly 14% according to oral glucose tolerance test (OGTT) results . The management of DM requires a significant consumption of healthcare resources, mainly in relation to the care of vascular complications. Among the late microvascular events which may develop in patients with DM, polyneuropathy (PN) is the most common and disabling, and is the leading cause of morbidity and mortality in these patients. Indeed, in Spain, the leading cause of neuropathy is DM, with its prevalence increasing with the presence of DM and other risk factors such as obesity.

PN is defined as the presence of symptoms and/or signs of peripheral nerve dysfunction in people with DM after the exclusion of other possible causes. The Toronto Panel Consensus on PN defined this disorder as "symmetrical, depending on large fibers, sensory-motor attributable to metabolic and micro vessel disorders, as a result of chronic hyperglycemia and other risk factors". In patients with PN, thin fibers (autonomic system - sweating) and thermal and tactile sensitivity are first affected, followed by the involvement of large fibers, presenting an altered vibrating sensation which eventually alters electromyography (EMG) patterns. Therefore, dysfunction of sweat reflex in small distal fibers is one of the earliest changes to be detected in these patients.

The most common clinical presentation of PN is distal symmetric polyneuropathy (DSPN), being predominantly sensory in 80% of cases. Pain is the most important symptom, being described as burning or flashing, lancinating, deep, and with frequent exacerbations during rest (4). Pain often affects the quality of life of these patients, and it is a frequent cause of depression and/or anxiety. Moreover, some patients may develop hypoesthesia, which may lead to severe foot lesions.

The prevalence of DSPN varies greatly according to the population, definition and detection method. The Rochester study, including more than 64,000 patients, reported the prevalence of PN to be between 66% and 59% for type1 DM and type 2 DM, respectively. The 3rd report of the Technical Study Group of Diabetes of the World Health Organization (WHO) described a prevalence of 40% (8), and 50% in patients with more than 25 years of DM evolution. Pirart et al. reported a prevalence ranging from 25 to 48% (7,10-17), while in Spain, Cabezas-Cerrato et al. published a figure of 24.1%. DSPN-related factors are: age, DM duration, metabolic control, male gender, acute myocardial infarction, hyperlipidemia (especially hypertriglyceridemia), smoking, and general cardiovascular risk factors . Puig et al. also included urinary albumin excretion as a risk factor of presenting DSPN.

The diagnosis of DSPN is commonly made based on signs and symptoms and usually includes the use of several questionnaires such as the Neuropathy Disability Score (NDS), the Neuropathy Symptoms Score (NSS) and the Michigan Neuropathy Instrument (MNI). These questionnaires are easy to perform and are reproducible, sensitive and adequate for use in a screening program. Additionally, It was included a short scale (UENS - Utah Early Neuropathy Scale) to screen early neuropathy . This sensitive, fast and practical test, has 5 items and their score ranges from 0 to 42 points.