Comparison of Weighted Performance Measurement and Dichotomous Thresholds for Glycemic Control in the Veterans Health Administration

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Abstract
OBJECTIVE—Quality measures of glycemic control using threshold values do not assess incremental quality improvement. We compared health care system performance using weighted continuous versus dichotomous measures for glycemic control. RESEARCH DESIGN AND METHODS—We performed retrospective cross-sectional analysis of chart abstraction data on 37,142 diabetic patients from 141 Veterans Health Administration medical centers in 2000–2001. RESULTS—Subjects per facility ranged from 163 to 740 (mean 263). Mean overall HbA1c (A1C) was 7.58%. A continuous measure for glycemic control was calculated based on percentage of maximal quality-adjusted life-years saved (QALYsS). Overall mean facility performance using the dichotomous measure was 62% <8% A1C (range 48–75%) and 39% <7% A1C (21–57%), in comparison with 45% maximal QALYsS (31–60%). Correlation between QALYsS and A1C thresholds of <8 (0.848) and <7 (0.838) for facility rankings was excellent; correlation between facility level performance using thresholds of <8 and 7% was poor (r = 0.13, P = 0.14). Comparison of facility rankings between the <7% dichotomous measure and the QALYsS-weighted measure showed that 22% changed their ranking by ≥2 deciles with marked changes in top and bottom deciles. CONCLUSIONS—Facility rankings vary by threshold or continuous methodology. However, because significant numbers of individuals are unable to reach “optimal” target goals (thresholds) even in clinical trials with extensive exclusion criteria, we propose that a continuous measure assessing improvement toward optimal A1C, rather than a pass/fail optimal target, is both a fairer assessment clinical practice and a more accurate reflection of population health improvement.