COMPONENTS OF VARIANCE FOR VIBRATORY AND THERMAL THRESHOLD TESTING INNORMAL AND DIABETIC SUBJECTS

Quantitative sensory testing (QST) is commonly used in the assessment of diabetic neuropathy. However, little data are available on the reli ability of tactile and thermal testing devices. Reproducibility of QST measures between centers has not been previously reported. This study was designed to validate QST testing procedures and determine if thes e devices are suitable for large scale multicenter clinical trials. Fi nger and toe vibratory (V-f, V-t) and thermal (T-f, T-t) thresholds we re determined for ten normal individuals by a two-alternative forced-c hoice procedure using the Optacon Tactile Tester (OTT) and Thermal Sen sitivity Tester (TST). Threshold measurements were reproducible betwee n technologists and had a day-to-day coefficient of variation of V-f 2 0%, V-t 23%, T-f 41%, and T-t 95%. Thresholds were determined for 140 normal individuals at six centers. Mean threshold values between cente rs were not significantly different. Center-to-center coefficents of v ariation (CV) were V-f 44%, V-t 45%, T-f 47%, and T-t 87%. There was n o significant difference in threshold measures with regard to sex, sid e studied, presence of calluses, or skin temperature. V-f thresholds s ignificantly correlated with age (p < 0.01). There was no correlation between either vibratory or thermal thresholds in normal individuals, and nerve conduction velocities (NCV). Thermal and vibratory threshold s were determined for 98 diabetic patients. Diabetic subjects without clinical evidence of neuropathy were not significantly different from normal individuals, but diabetic patients with neuropathy had increase d thresholds compared to normals (p < 0.05). We conclude that thermal and vibratory threshold testing with the OTT and TST yields reproducib le measurements in normal individuals and provides an objective measur e of clinical diabetic neuropathy that is well suited for multicenter trials.