Evaluation of regional variation in total, major, and minor amputation rates in a national health-care system

Background. Health-care systems need actionable information on amputation rates in order to improve foot-care delivery. Objective. To evaluate regional variation in total, major, and minor amputation rates using individual-level data. Methods. This was a retrospective cohort study of Veterans Health Administration users with diabetes who were Medicare enrolled between fiscal years 1998 and 2000 (10/1/1997-9/30/2000). The outcome was outlier status, based upon observed-to-expected ratios, for total, major, and minor amputations of 22 regional networks in fiscal year 2000. Results. 331,806 patients incurred a total of 4,037 (12.2 per 1000; range 9.3-16.7 across networks) amputations in fiscal year 2000: 2,271 major amputations (6.8 per 1000; 4.7-9.1) and 1,766 minor amputations (5.3 per 1000; 3.9-7.6). All network outliers based upon the total amputation observed-to-expected ratio were also outliers based on major amputation observed-to-expected ratio. However, two of the five non-outliers based on total amputations were outliers based on major amputations. Simultaneous evaluation of major and minor amputation observed-to-expected ratios demonstrated four patterns of dual outlier status among networks: two networks had lower than expected minor and major amputation rates; two had higher than expected minor and major amputation rates; one network was lower than expected by major but higher by minor amputation rate; one was higher than expected by major but lower by minor amputation rate. Conclusions. Simultaneous evaluation of major and minor amputation rates identifies different patterns of regional outlier status compared to total or major amputation rates alone. This strategy may facilitate targeted evaluations of health-care processes and structures.