Validation of a Novel Point-of-Care Nerve Conduction Device for the Detection of Diabetic Sensorimotor Polyneuropathy

Abstract

OBJECTIVE -The diagnosis of diabetic sensorimotor polyneuropathy using objective electrophysiological tests is hindered by limited access to the specialized laboratories and technicians that perform and interpret them. We evaluated the performance characteristics of a novel portable and automated point-of-care nerve conduction study device, which can be operated by nontechnical personnel, and compared it with conventional nerve conduction studies performed in a specialist setting.RESEARCH DESIGN AND METHODS -Seventy-two consecutive patients with diabetes (8 type 1, 64 type 2) from a diabetes and a neuropathy outpatient clinic were evaluated concurrently with conventional nerve conduction studies (the reference standard) and the pointof-care device for sural nerve function (sural nerve amplitude potentials in microvolts [V]).RESULTS -Sural nerve amplitude potentials measured by the point-of-care device shared very strong correlation with the reference standard (Spearman's correlation coefficient 0.95, P Ͻ 0.001). The Bland and Altman method yielded agreement despite a small systematic underestimation by the point-of-care device of 1.2 Ϯ 3.4 V. Despite this small systematic bias, the sensitivity and specificity of normal and abnormal sural nerve amplitude potentials measured by the point-of-care device for the detection of diabetic sensorimotor polyneuropathy defined by standard clinical and electrophysiological criteria were 92 and 82%, respectively.CONCLUSIONS -A novel point-of-care device has excellent diagnostic accuracy for detecting electrophysiological abnormality in the sural nerve of patients who have diabetes. This automated device represents an alternative to conventional nerve conduction studies for the diagnosis of diabetic sensorimotor polyneuropathy. Diabetes Care 29:2023-2027, 2006D iabetic sensorimotor polyneuropathy is by far the most common neurological complication of diabetes, as it imparts a lifetime risk of up to 50% (1,2). It represents an insidious and progressive process that begins with a long asymptomatic stage during which identification and management is challenging (3,4). It is important to identify neuropathy early in the course of its development, even in the asymptomatic stages, because the disease process predictably progresses to produce extreme morbidity (2,5) and health care costs (6,7) that arise from pain, imbalance, foot deformity, and the late-stage consequences of infection, ulceration, and amputation. Many of these consequences are thought to be preventable if appropriate clinical management (the combination of early identification, intensification of glycemic control, and surveillance for foot complications) is instituted (8 -10).Clinical practice guidelines for the care of people who have diabetes recommend annual screening for diabetic sensorimotor polyneuropathy using simple tools such as the 10-g Semmes-Weinstein monofilament or the 128-Hz vibration tuning fork (11,12). These simple tests predict the presence of neuropathy defined by electrophysiological criteria (n...

NC-stat for the diagnosis of diabetic polyneuropathy

“…In patients with type 1 and type 2 DM, this original device again resulted in reasonable agreement with conventional NCS parameters (the reference standard) performed by electromyography technicians, and it could accurately identify DPN in both type 1 and type 2 DM patients [12,13]. Spearman coefficients for correlation between the SNAP of the point-of-care and conventional NCS was high: 0.95 (with p < 0.001) [12].…”

“…Spearman coefficients for correlation between the SNAP of the point-of-care and conventional NCS was high: 0.95 (with p < 0.001) [12]. However, Bland and Altman statistical method showed a slight underestimation of SNAP by an average of 1.2 ± 3.4 μV with the point-of-care device in comparison with the reference method [12]. In spite of this systematic bias (which is reported as clinically unimportant by the authors), quantitative agreement as demonstrated by the Bland and Altman method was strong [12].…”

“…Spearman coefficients for correlation between the SNAP of the point-of-care and conventional NCS was high: 0.95 (with p < 0.001) [12]. However, Bland and Altman statistical method showed a slight underestimation of SNAP by an average of 1.2 ± 3.4 μV with the point-of-care device in comparison with the reference method [12].…”

“…The clinical implication of this is that a borderline result should be repeated. Second, a small systematic bias for SNAP [12] or SNCV measurement has been reported [7]. A third limitation relates to a number of reasons, such as anatomical variations of sural nerve, severe edema, excessive adipose tissue, poor skin preparation and device misplacement, which might produce non-recordable measurements (SNAP less than 1.5 μV).…”

“…However, Bland and Altman statistical method showed a slight underestimation of SNAP by an average of 1.2 ± 3.4 μV with the point-of-care device in comparison with the reference method [12]. In spite of this systematic bias (which is reported as clinically unimportant by the authors), quantitative agreement as demonstrated by the Bland and Altman method was strong [12]. Specifically, this novel device resulted in sufficient sensitivity and specificity of 88% and 82%, respectively [13].…”