Cutaneous thermal thresholds in normal subjects and diabetic patients without symptoms of peripheral neuropathy

An automated system operating on the Peltier principle and using a two-alternative forced-choice testing technique was applied to measure the heat and cold thermal thresholds (HT and CT) in 63 normal subjects and 68 diabetic patients who had no clinical symptoms of peripheral neuropathy. To compare large and small nerve fiber functions, 34 of the diabetic group were also tested for vibration perception threshold (VPT) and nerve conduction velocity (NCV). The testing algorithm of the devices selected for used, including reference temperature and number of turns, was investigated for assessment of variability and reliability. The age effect on thermal thresholds was found in the normal group (p less than 0.001). There was a significant difference between HT and CT in an individual (p less than 0.01). CT was greater than HT in 68% of the subjects. The diabetic group had significantly higher thermal thresholds than the normal group (HT, 0.30 +/- 0.32 degree C vs 0.10 +/- 0.05 degree C, p less than 0.005; CT, 0.39 +/- 0.43 degree C vs 0.15 +/- 0.09 degree C, p less than 0.005). Thermal thresholds greater than the linear regression estimate for age plus three standard errors of estimate were defined as abnormal. The abnormality rate in diabetics was 33.8% for HT and 22.1% for CT. Of the 34 patients, 91.1% had abnormal results in at least one of the three tests: 47.1% abnormal for HT or CT, 67.6% for VPT, and 26.4% for NCV. No correlation existed between the thermal threshold and VPT (p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)