Routine nerve conduction study (NCS) can only be used to evaluate the function of large fibers, and the results of NCS are often normal in patients with distal sensory polyneuropathy. The measurement of the current perception threshold (CPT) has been reported to represent a variety of peripheral nerve fiber functions. This study was performed to investigate the value of measuring CPT in patients with diabetic sensory polyneuropathy who have no abnormalities in routine NCS.

Twenty-seven diabetic patients with sensory polyneuropathy and normal routine NCS and 18 age-matched control subjects participated in this study. The CPT was measured on the unilateral index finger and great toe of each subject at frequencies of 5 Hz, 250 Hz, and 2,000 Hz.

CPT values were significantly higher in the patient group than in the control group, especially with stimuli at the lowest frequency of 5 Hz ( p < 0.05). There were significant correlations between the CPT values obtained at three different frequencies in the patient group, whereas the correlation was only significant in the pair of 250 Hz/5 Hz (both in the hands and feet), and in the pair of 2,000 Hz/250 Hz (in the feet) for the control group.

Our data suggest that the CPT test, especially at a stimuli frequency of 5 Hz, may be a useful screening tool for diabetic polyneuropathy in patients who show no abnormalities in routine NCS.