Neuropad indicator test for diagnosis of sudomotor dysfunction in type 2 diabetes

Neuropad is a new indicator test used to diagnose sudomotor dysfunction, a component of autonomic neuropathy. In this cross-sectional study, Neuropad is evaluated and compared with corrected QT (QT c), another test used in the diagnosis of autonomic neuropathy. The indicator test measures sweat production on the basis of a color change of cobalt (II) chloride solution from blue to pink upon absorption of water. This study involved 105 patients (43 men, 62 women) with type 2 diabetes with a mean age of 56.2+/-11.5 y and a mean disease duration of 10.0+/-6.3 y. Age, sex, disease duration, glycosylated hemoglobin, and QT c were compared between patients with normal and abnormal test results. The QT c interval was measured and the new indicator test was applied in all patients. The 2 tests were compared, and the sensitivity, specificity, positive predictive value, and negative predictive value for the indicator test were calculated. Autonomic neuropathy was diagnosed in 40 patients (38.1%) with QT c interval measurement and in 72 patients (68.6%) with the new indicator test (P=.001). The sensitivity, specificity, positive predictive value, and negative predictive value for the indicator test were 87.5%, 43.1%, 48.6%, and 84.8%, respectively. Patients with abnormal test outcomes had longer QT c than those whose test results were normal (0.433 vs 0.398 s; P=.002). Study results suggest that the new indicator test has an acceptable sensitivity but a low specificity and is not superior to other tests in the diagnosis of sudomotor dysfunction.