Sudomotor neuropathy is associated with reduction of plantar sweating and contributes to the pathogenesis of diabetic foot ulcers. The aim of the present study was to evaluate the new indicator test for sudomotor function (Neuropad) in the diagnosis of peripheral neuropathy among type 2 diabetic patients. This study included 104 type 2 diabetic patients (51 men) with a mean age of 64.2+/-5.6 years and a mean diabetes duration of 12.8+/-3.7 years. Peripheral neuropathy was diagnosed by means of the Diabetic Neuropathy Index (DNI). Sudomotor neuropathy was assessed by means of colour change in the indicator test. Peripheral neuropathy was diagnosed in 71 patients (68.3 %). Sudomotor neuropathy was diagnosed in 67 patients (94.4 %) with peripheral neuropathy and in 10 patients (30.3 %) without peripheral neuropathy (p=0.0001). Compared with DNI, sensitivity of the indicator test for diagnosing peripheral neuropathy was 94.4 % and specificity was 69.7 %. Overall prevalence of neuropathy was higher using the indicator test (77 patients, 74.0 %) than using the DNI (71 patients, 68.3 %). Time until complete colour change of the indicator test was 23.8+/-6.7 min in patients with peripheral neuropathy and 7.7+/-1.2 min in patients without peripheral neuropathy (p=0.001). Among patients with peripheral neuropathy, time until complete colour change of the indicator test was 14.2+/-1.9 min in those with a DNI value between 2.5 and 4.5, while it was 32.8+/-2.6 min in those with a DNI value between 5 and 8 (p=0.003).
Conclusions: Use of the new indicator test has a very high sensitivity in detection of diabetic peripheral neuropathy. Sudomotor dysfunction can be demonstrated in a considerable part of patients with normal clinical examination. Time until complete colour change of the indicator test is associated with severity of peripheral neuropathy.