Cost sharing and HEDIS performance.

Physicians, health plans, and health systems are increasingly evaluated and rewarded based on Health Plan Effectiveness Data and Information Set (HEDIS) and HEDIS-like performance measures. Concurrently, employers and health plans continue to try to control expenditures by increasing out-of-pocket costs for patients. The authors use fixed-effect logit models to assess how rising copayment rates for physician office visits and prescription drugs affect performance on HEDIS measures. Findings suggest that the increase in copayment rates lowers performance scores, demonstrating the connection between financial aspects of plan design and quality performance, and highlighting the potential weakness of holding plans and providers responsible for performance when payers and benefit plan managers also influence performance. Yet the effects are not consistent across all domains and, in many cases, are relatively modest in magnitude. This may reflect the HEDIS definitions and suggests that more sensitive measures may capture the impact of benefit design changes on performance.