Variability in function measurements of three sensory foot nerves in neuropathic diabetic patients

We have examined the variability in function measurements of three sensory foot nerves in neuropathic diabetic patients and have compared them to measurements from healthy non-diabetic subjects. Sixty-six healthy, non-diabetic subjects (30 (45%) males, mean age 56 years (range, 21-84 years)) and 61 age and sex matched diabetic patients (33 (54%) males, mean age 55 years (range, 34-78 years) Type 1 diabetes mellitus (DM), mean duration of DM 24 years (range, 2-48 years)) were tested. Current perception threshold (CPT) at 250 Hz was employed to test the sensory function of three nerves: superficial peroneal, sural and posterior tibial. The vibration perception threshold, (VPT) and the cutaneous perception threshold (CCPT) were also assessed at the great toe. According to the results of the neuropathy disability score (NDS), mild neuropathy was present in 8 (13%) patients, moderate in 33 (54%) and severe in 20 (33%). In both groups the CPT of the posterior tibial nerve was higher than the other two nerves (P < 0.0001) while no difference was found between the superficial peroneal and sural nerves (P = NS). CPT was different between the two feet at the superficial peroneal nerve in 39 (64%) diabetic patients and 34 (52%) controls (P = NS), at the sural nerve in 40 (65%) and 45 (68%) (P = NS), and at the posterior tibial in 36 (59%) and 33 (50%), respectively (P = NS). VPT was different by more than 10% at the great toes in 26 (43%) diabetic subjects and CCPT in 21 (34%). We conclude that although there is variation in sensory nerve function tests in diabetic patients this is similar to that noticed in healthy subjects. The great variability of all quantitative sensory testing indicates that more than one site should be tested.