John E. Lewis, Steven E. Atlas, Ammar Rasul, Ashar Farooqi, Laura Lantigua, Oscar L. Higuera, Andrea Fiallo, Lianette Laria, Renata Picciani, Ken Wals, Zohar Yehoshua, Armando Mendez, Janet Konefal, Sharon Goldberg, Judi Woolger

Diabetes-associated microvascular complications such as retinopathy and neuropathy often lead to end-organ and tissue damage. Impaired skin microcirculation often precedes the detection of other advanced diabetic complications. The ANS-1 system contains a redesigned sympathetic skin response (ANS-1 SSR) device that measures sudomotor function, a photoplethysmography sensor, and a blood pressure device to comprehensively assess cardiac autonomic neuropathy and endothelial dysfunction. The purpose of this study was to determine the relationships between the ANS-1 SSR amplitude measured at the: (a) negative electrode (Nitric Oxide [NO] Sweat Peak) with microvascular diseases and associated vascular blood markers and (b) positive electrode (iSweat Peak) with C fiber function. All participants (healthy controls n = 50 and retinopathy patients n = 50) completed the ANS-1 system evaluation and a basic sociodemographic and medical history questionnaire, including a quality of life measure (SF-36). A small sample of blood was drawn to determine levels of homocysteine, blood urea nitrogen (BUN), C-reactive protein (CRP), and fibrinogen. Symptoms of peripheral foot neuropathy were assessed with a scale from 1 (none) to 10 (the worst). We used Spearman rank correlations, independent samples t-tests, and receiver operating characteristic curves to determine the specificity and sensitivity of the NO Sweat Peak as a potential screening marker of retinopathy. The ANS-1 System Cardiometabolic Risk Score and all indicators of quality of life on the SF-36, other than Emotional Role Functioning, were significantly worse in the retinopathy patients. The sudomotor response marker NO Sweat Peak had a sensitivity of 88% and a specificity of 68% (Area Under the Curve = 0.81, p < 0.0001) to detect retinopathy. The NO Sweat Peak response marker inversely correlated with BUN (ρ = -0.41, p < 0.0001), homocysteine (ρ = -0.44, p < 0.0001), fibrinogen (ρ = -0.41, p < 0.0001), the Cardiac Autonomic Neuropathy score (ρ = -0.68, p < 0.0001), and the heart rate variability Total Power (ρ = -0.57, p < 0.0001), and it positively correlated with the Photoplethysmography Index (PTGi; ρ = 0.53 p < 0.0001). The ANS-1 system sudomotor response marker iSweat Peak inversely correlated with the severity of symptoms on the peripheral neuropathy scale (ρ = -0.56, p < 0.0001). The results of the study show that this new method of measuring sympathetic skin response should be useful for detecting the earliest manifestations of microvascular disease and symptoms of C fiber dysfunction.