Prediction of Diabetic Foot Ulcer Occurrence Using Commonly Available Clinical Information

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Abstract
OBJECTIVE—The ability of readily available clinical information to predict the occurrence of diabetic foot ulcer has not been extensively studied. We conducted a prospective study of the individual and combined effects of commonly available clinical information in the prediction of diabetic foot ulcer occurrence. RESEARCH DESIGN AND METHODS—We followed 1,285 diabetic veterans without foot ulcer for this outcome with annual clinical evaluations and quarterly mailed questionnaires to identify foot problems. At baseline we assessed age; race; weight; current smoking; diabetes duration and treatment; HbA1c (A1C); visual acuity; history of laser photocoagulation treatment, foot ulcer, and amputation; foot shape; claudication; foot insensitivity to the 10-g monofilament; foot callus; pedal edema; hallux limitus; tinea pedis; and onychomycosis. Cox proportional hazards modeling was used with backwards stepwise elimination to develop a prediction model for the first foot ulcer occurrence after the baseline examination. RESULTS—At baseline, subjects were 62.4 years of age on average and 98% male. Mean follow-up duration was 3.38 years, during which time 216 foot ulcers occurred, for an incidence of 5.0/100 person-years. Significant predictors (P ≤ 0.05) of foot ulcer in the final model (hazard ratio, 95% CI) included A1C (1.10, 1.06–1.15), impaired vision (1.48, 1.00–2.18), prior foot ulcer (2.18, 1.61–2.95), prior amputation (2.57, 1.60–4.12), monofilament insensitivity (2.03, 1.50–2.76), tinea pedis (0.73, 0.54–0.98), and onychomycosis (1.58, 1.16–2.16). Area under the receiver operating characteristic curve was 0.81 at 1 year and 0.76 at 5 years. CONCLUSIONS—Readily available clinical information has substantial predictive power for the development of diabetic foot ulcer and may help in accurately targeting persons at high risk of this outcome for preventive interventions.