Assessing Quality of Diabetes Care by Measuring Longitudinal Changes in Hemoglobin A1c in the Veterans Health Administration

Abstract

Context. A1c levels are widely used to assess quality of diabetes care provided by health care systems. Currently, cross‐sectional measures are commonly used for such assessments. Objective. To study within‐patient longitudinal changes in A1c levels at Veterans Health Administration (VHA) facilities as an alternative to cross‐sectional measures of quality of diabetes care. Design. Longitudinal study using institutional data on individual patient A1c level over time (October 1, 1998–September 30, 2000) with time variant and invariant covariates. Setting. One hundred and twenty‐five VHA facilities nationwide, October 1, 1998–September 30, 2000. Patients. Diabetic veteran users with A1c measurement performed using National Glycosylated Hemoglobin Standardization Project certified A1c lab assay methods. Exposures. Characteristics unlikely to reflect quality of care, but known to influence A1c levels, demographics, and baseline illness severity. Main Outcome Measure. Monthly change in A1c for average patient cared for at each facility. Results. The preponderance of facilities showed monthly declines in within‐patient A1c over the study period (mean change of −0.0148 A1c units per month, range −0.074 to 0.042). Individual facilities varied in their monthly change, with 105 facilities showing monthly declines (70 significant at .05 level) and 20 showing monthly increases (5 significant at .05 level). Case‐mix adjustment resulted in modest changes (mean change of −0.0131 case‐mix adjusted A1c units per month, range −0.079 to 0.043). Facilities were ranked from worst to best, with attached 90 percent confidence intervals. Among the bottom 10 ranked facilities, four remained within the bottom decile with 90 percent confidence. Conclusions. There is substantial variation in facility‐level longitudinal changes in A1c levels. We propose that evaluation of change in A1c levels over time can be used as a new measure to reflect quality of care provided to populations of individuals with chronic disease.

Impact of Self-Reported Patient Characteristics Upon Assessment of Glycemic Control in the Veterans Health Administration

“…To minimize any impact of difference in A1C methodologies, we eliminated medical centers that used A1C methodologies in fiscal year 2000 that were not certified by the National Glycohemoglobin Standardization Program as previously described (16). Although the Health Plan Employee Data and Information Set (HEDIS) measures for glycemic control count A1C not measured as being greater than the threshold value, we also excluded individuals at remaining medical centers who did not have laboratory tests performed in the VHA both to focus our study upon the influence of patient characteristics on glycemic control and because administrative data could not capture laboratory tests performed outside the VHA and recorded in progress notes.…”

Advancing Evidence-Based Care For Diabetes: Lessons From The Veterans Health Administration

“…In Exhibit 2, case-mix-adjusted glycosylated hemoglobin (HbA1c) values among veterans with diabetes decreased by -0.314 percent (range -1.90 to 1.03, p < 0.0001) over two years, indicating improved glycemic control over time, rather than simply the enrollment of healthier veterans. 15 These findings provide a convincing demonstration of effective diabetes care.…”

Pharmacoepidemiology of insulin initiation in diabetes care

“…Fourth, longitudinal modelling of hemoglobin A 1c in fixed cohorts can minimize biases inherent in estimating trends from cross-sectional data. 10 Finally, total costs should be evaluated, but only in the context of overall health outcomes.…”