A Comparison of the New Indicator Test for Sudomotor Function (Neuropad®) with the Vibration Perception Threshold and the Clinical Examination in the Diagnosis of Peripheral Neuropathy in Subjects with Type 2 Diabetes

Peripheral neuropathy remains a major cause of morbidity and is a cardinal factor in the pathogenesis of diabetic foot ulceration. The aim of the present study was to compare the new indicator test for sudomotor function (Neuropad ® ) with the vibration perception threshold (VPT) and the clinical examination in the diagnosis of peripheral neuropathy in subjects with type 2 diabetes. This study included 154 type 2 diabetic patients (76 men) with a mean age of 64.3±7.3 years and a mean diabetes duration of 12.8±4.3 years. Neuropathy was diagnosed clinically using the Neuropathy Disability Score (NDS). The VPT was measured with a neurothesiometer, values25Volts being classified as abnormal. Sudomotor function was evaluated by the indicator test. Sensitivity of the indicator test for neuropathy was 97.8% and specificity was 67.2%. Sensitivity and specificity of VPT for neuropathy were 78.9% and 85.9% respectively. A significant correlation was shown between time to colour change of the indicator test and VPT (r s =0.889, p>0.001). CONCLUSIONS: Both the indicator test and the VPT have a high sensitivity for neuropathy. Sensitivity is higher with the indicator test, but specificity is higher with VPT. Time until complete colour change of the indicator test shows a positive correlation with VPT. Thus, the indicator test appears to be a useful additional diagnostic tool of neuropathy, particularly suitable for screening and self-examination, in type 2 diabetes. The correlation between time to colour change of the indicator test and VPT is interesting and merits investigation in a prospective study.