HEDIS performance trends in Medicare managed care.

The authors analyzed performance trends between 1996 and 1998 for health plans in the Medicare managed care program. Four measures from the Health Employer Data and Information Set (HEDIS) were used to track performance changes: adult access to preventive/ambulatory health services, beta blocker treatment following heart attacks, breast cancer screening, and eye exams for people with diabetes. Using a cohort analysis at the health plan level, statistically significant improvements in performance rates were observed for all measures. Health plans exhibiting relatively poor performance in 1996 accounted for the largest share of overall improvement in these measures across years.