A FOOT RISK CLASSIFICATION-SYSTEM TO PREDICT DIABETIC AMPUTATION IN PIMA-INDIANS

OBJECTIVE - To quantify the contribution of various risk factors to th e risk of amputation in diabetic patients and to develop a foot risk s coring system based on clinical data. RESEARCH DESIGN AND METHODS - A population-based 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) h ad 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 re cords were reviewed to determine risk conditions and health status bef ore 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 r atio [OR] 6.5, 95% CI 2.6-15), and people with diabetic eye, renal, or cardiovascular disease were more likely to undergo amputation than th ose without (OR 4.6, 95% CI 1.7-12). The risk of amputation was almost equally associated with these foot risk factors. peripheral neuropath y, peripheral vascular disease, bony deformities, and a history of foo t ulcers. After controlling for demographic differences and diabetes s everity, the ORs for amputation with one loot 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 th ree or four risk factors, 9.7 (95% CI 6.3-14.8). CONCLUSIONS - Male se x, end-organ complications of eye, heart, and kidney, and poor glucose control were associated with a higher amputation rate. Peripheral neu ropathy, peripheral vascular disease, deformity, and a prior ulcer wer e similarly equally associated with an increased risk of lower extremi ty amputation.