A Foot Risk Classification System to Predict Diabetic Amputation in Pima Indians

Abstract

OBJECTIVE To quantify the contribution of various risk factors to the risk of amputation in diabetic patients and to develop a foot risk scoring system based on clinical data. RESEARCH DESIGN AND METHODS A population case-control study was undertaken. Eligible subjects were 1) 25-85 years of age, 2) diabetic, 3) 50% or more Pima or Tohono O'odham Indian, 4) lived in the Gila River Indian Community, and 5) had had at least one National Institutes of Health research examination. Case patients had had an incident lower extremity amputation between 1983 and 1992; control subjects had no amputation by 1992. Medical records were reviewed to determine risk conditions and health status before the pivotal event that led to the amputation. RESULTS Sixty-one people with amputations were identified and compared with 183 control subjects. Men were more likely to suffer amputation than women (odds ratio [OR] 6.5, 95% CI 2.6–15), and people with diabetic eye, renal, or cardiovascular disease were more likely to undergo amputation than those without (OR 4.6, 95% CI 1.7–12). The risk of amputation was almost equally associated with these foot risk factors: peripheral neuropathy, peripheral vascular disease, bony deformities, and a history of foot ulcers. After controlling for demographic differences and diabetes severity, the ORs for amputation with one foot risk factor was 2.1 (95% CI 1.4–3.3), with two risk factors, 4.5 (95% CI 2.9–6.9), and with three or four risk factors, 9.7 (95% CI 6.3–14.8). CONCLUSIONS Male Sex, end-organ complications of eye, heart, and kidney, and poor glucose control were associated with a higher amputation rate. Peripheral neuropathy, peripheral vascular disease, deformity, and a prior ulcer were similarly equally associated with an increased risk of lower extremity amputation.