Hemoglobin A1c Testing and Amputation Rates in Black, Hispanic, and White Medicare Patients

Major (above-knee or below-knee) amputation is a complication of diabetes and is seen more common among black and Hispanic patients. While amputation rates have declined for patients with diabetes in the last decade, it remains unknown if these improvements have equitably extended across racial groups and if measures of diabetic care, such as hemoglobin A1c testing, are associated with these improvements. We set out to characterize secular changes in amputation rates among black, Hispanic, and white patients, and to determine associations between hemoglobin A1c testing and amputation risk.

We identified 11,942,840 Medicare patients (55% female) with diabetes over the age of 65 years between 2002 and 2012 and followed them for a mean of 6.6 years. Of these, 86% were white, 11.5% were black, and 2.5% were Hispanic. We recorded the occurrence of major amputation and hemoglobin A1c testing during this time period and studied secular changes in amputation rate by race (black, Hispanic, and white). Finally, we examined associations between amputation risk and hemoglobin A1c testing. We measured both the presence of any testing and testing consistency using 3 categories: poor consistency (hemoglobin A1c testing in 0-50% of years), medium consistency (testing in 50-90% of years), and high consistency (testing in >90% of the years in the cohort).

Between 2002 and 2012, the average major lower-extremity amputation rate in diabetic Medicare patients was 1.78 per 1,000 per year for black patients, 1.15 per 1,000 per year for Hispanic patients, and 0.56 per 1,000 per year for white patients (P < 0.001). Over the study period, the incidence of major amputation in Medicare patients with diabetes declined by 54%, from 1.15 per 1,000 in 2002 to 0.53 per 1,000 in 2012 (rate ratio = 0.53, 95% CI = 0.51-0.54). The reduction in amputation rate was similar across racial groups: 52% for black patients, 61% for Hispanic patients, and 55% for white patients. In multivariable analysis adjusting for patient characteristics, including race, any use of hemoglobin A1c testing was associated with a 15% decline in amputation risk (hazard ratio, 0.85; 95% CI, 0.83-0.87; P < 0.001). High consistency hemoglobin A1c testing was associated with a 39% decline in amputation (hazard ratio, 0.61; 95% CI, 0.59-0.62; P < 0.0001).

Although more frequent among racial minorities, major lower-extremity amputation rates have declined similarly across black, Hispanic, and white patients over the last decade. Hemoglobin A1c testing, particularly the consistency of testing over time, may be an effective component metric of longitudinal quality measures toward limiting amputation in all races.