Usefulness of a new indicator test for the diagnosis of peripheral and autonomic neuropathy in patients with diabetes mellitus

Aims The aim of the present study was to assess the performance of a new indicator test (NIT), based on the measurement of sweat production after exposure to dermal foot perspiration, in the diagnosis of both peripheral sensorimotor polyneuropathy (PSN) and autonomic neuropathy in patients with diabetes. Methods One hundred and seventeen diabetic patients were examined. PSN was assessed using the neuropathy symptoms score, the neuropathy disability score and the vibration perception threshold. Cardiac autonomic neuropathy (CAN) was assessed using the battery of the four classical standardized tests proposed by Ewing et al., Diabetes Care 1985; 8: 491-498. Sudomotor dysfunction was assessed using the NIT. Results Fifty patients (42.7%) had PSN and 44 patients (37.6%) had CAN. Of the 50 patients with PSN, 43 had a positive NIT (sensitivity 86%) and, out of the 67 patients without PSN, a negative NIT was obtained in 45 patients (specificity 67%). The positive and the negative predictive value of the NIT in detecting PSN were 66.2 and 86.5%, respectively. The sensitivity and specificity of NIT in detecting CAN was 59.1 and 46.5%, respectively. In the case of severe CAN, the sensitivity was increased to 80.9% and the specificity to 50%. Conclusions The NIT has good sensitivity and negative predictive value for diagnosis of PSN and can be used as a screening method for detection of this complication in patients with diabetes. In addition, the test has a low sensitivity for detection of autonomic neuropathy in patients with milder forms of CAN.