BACKGROUND: Lower-limb amputation is the most severe non-fatal consequence of critical limb ischemia caused by peripheral artery disease (PAD). It is associated with poor cardiovascular and diabetes risk profiles, and with high rates of myocardial infarction and stroke, yet its incidence and epidemiology is poorly described. Previous work in Minnesota during 2005-2008 demonstrated large variation in the rate of lower-limb amputation by counties. The purpose of this work is to update this surveillance methodology and explore patterns at the sub-county level to identify disparities and potential targets in a push to disseminate new PAD identification and treatment guidelines.
METHODS: We assessed the incidence of lower-limb ischemic amputation using all inpatient hospital discharge claims in Minnesota from 2010 through 2014. We identified lower-limb ischemic amputations from ICD-9 procedure codes by modifying the AHRQ Prevention Quality Indicator #16 (Rate of Lower-Extremity Amputation Among Patients with Diabetes) by also including patients with known vascular disease. Age-adjusted hospitalization rates for lower-limb amputation were calculated by Primary Care Service Areas (PCSA) or zip codes, when possible. Geographic and demographic differences in amputation events are described. We compared these results to the hospitalization rates for other acute cardiovascular events Acute Myocardial Infarction (AMI) and stroke.
RESULTS: There were 3,600 lower-limb amputations in Minnesota during 2010-2014, yielding an age-adjusted annual hospitalization rate for ages 18 plus of 17.5 per 100,000 (95% CI: 16.9-18.0). Out of 143 PCSA or zip code geographies in Minnesota, 23 had amputation rates significantly higher than the state rate, with 12 areas experiencing rates at least twice as high. These 23 communities had lower median incomes, higher poverty rates, lower levels of educational attainment, and were more likely to be racially-diverse than communities with rates lower than or no different than the state. These communities were located in both the Twin Cities and in small towns and rural areas in the northern half of Minnesota. Similar patterns were observed for hospitalizations due to AMI and stroke. All but 2 of the high amputation rate communities experienced elevated AMI or stroke rates as well.
CONCLUSIONS: Geographic disparities in the lower-limb amputation rate in Minnesota were similar to disparities in the hospitalization rates for AMI and stroke. Communities experiencing the highest amputation rates had lower access to preventive and speciality services. These results highlight the need to improve public awareness of PAD and actively encourage clinical providers to adopt the newest PAD identification and treatment guidelines.