Does Rapid Diffusion of HbA1c Testing Affect Amputation Rates?

Background: The association of speed of diffusion of Hemoglobin A1C (hbA1c) testing with temporal changes in outcomes of primary importance to patients with diabetes, such as amputation, remains an issue of debate. We investigated these correlations. Methods: We performed a retrospective cohort study of diabetics, based on Medicare fee-for-service claims data from 2002 to 2012. We examined the association of the rate of diffusion of HbA1c testing with changes in amputation rates. Our unit of analysis was the hospital referral region (HRR), a definition of tertiary care markets defined in the Dartmouth Atlas of Health Care. Results: From the 11 096 270 diabetics followed in our study for a mean follow-up of 4.1 years, 106 340 (0.96%) underwent lower extremity amputations. The speed of diffusion of HbA1c testing had a moderate association with the speed of diffusion of lower extremity amputations, after adjusting for multiple factors including baseline regional amputation and testing rates (adjusted difference, -0.7%; 95% confidence interval, -1.0% to -0.3%). The risk-adjusted HRR-level speed of diffusion of testing demonstrated significant correlation with the risk-adjusted HRR-level diffusion of amputations (r = .250, P < .001). Conclusions: We observed a moderate association of the speed of diffusion of HbA1c testing with the speed of diffusion of lower extremity amputations among Medicare patients with diabetes. Improvements in performance on quality metrics such as HbA1c testing may not immediately translate into tangible patient outcomes.