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, values > 25Volts 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 (rs=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.