The value of the Neurometer in assessing diabetic neuropathy by measurement of the current perception threshold

Abstract

The Neurometer is a relatively new device for assessing neuropathy by measuring current perception threshold (CPT). The study aim was to assess the ability of the Neurometer to distinguish between different types of nerve fibre damage by using different frequencies (2000 Hz, 250 Hz, and 5 Hz) of electric stimulus (high frequencies for large fibres and low frequencies for small fibres) and comparing the results with standard sensory tests of vibration perception threshold (VPT) and thermal perception threshold (TPT). CPT was determined on index finger and great toe of 51 patients with diabetic neuropathy and 28 non-diabetic control subjects, age and sex matched. CPT in neuropathic patients could be distinguished from controls at all three frequencies in both feet and hands (p < 0.05). The best correlation was found between CPT at 2000 Hz and VPT (r = 0.48, p < 0.001) in the feet suggesting a degree of neuroselectivity. Internal correlations between CPT at the three frequencies showed the weakest correlation between CPT at 2000 Hz and 5 Hz (r = 0.27, p < 0.005), suggesting also that possibly different types of fibres were examined. CPT reproducibility was better in control (CV = 6.4-27.7%), than in neuropathic subjects (CV = 28.4-52.3%), although the coefficient of variation was comparable to that of standard tests of sensory function, VPT and TPT. The Neurometer is a simple instrument to use in clinical practice. It has a degree of neuroselectivity but like all subjective sensory tests has a large variability.