Objective: To investigate longitudinally prognostic factors for foot ulceration in a large population of diabetic patients with established neuropathy.
Research design and methods: A double-blind multicenter study of a potential new agent for diabetic neuropathy provided the opportunity for this 1-year investigation since intervention demonstrated no efficacy in the condition. A total of 1,035 patients with NIDDM and IDDM were included. Inclusion criteria were vibration perception threshold (VPT) at the great toe > or = 25 V in at least one foot and < or = 50 V in both feet, normal peripheral circulation, and no previous foot ulceration. VPT and clinical components of the Michigan diabetic polyneuropathy (DPN) score were assessed at baseline and subsequent visits.
Results: After 1 year, the incidence of first foot ulcers for the total population was 7.2%. Neuropathy parameters were the same between the treatment and placebo groups at baseline and were unchanged at 1 year; therefore, baseline data were combined for multiple regression analysis. VPT, age, and Michigan DPN scores for muscle strength and reflexes were significant independent predictors for first foot ulceration (P < 0.01). For each 1-U increase in VPT values at baseline, the hazard of the first foot ulcer increased by 5.6%. Similarly, for each 1-U increase in muscle strength and reflex components of the Michigan DPN scores, the hazard of the first foot ulcer increased by 5.0%.
Conclusions: Tests of VPT and Michigan DPN scores for muscle strength and reflexes are useful clinical predictors for foot ulceration in diabetic patients with established neuropathy. The rate of subsequent ulceration in the following year was alarmingly high, however, despite standardized foot care education at baseline and regular follow-up visits.