Impact of sociodemographic case mix on the HEDIS measures of health plan quality

BACKGROUND. The widely used Health Plan Employer Data and Information Set ( HEDIS) measures may be affected by differences among plans in sociodemograp hic characteristics of members. OBJECTIVE. The objective of this study was to estimate effects of geographi cally linked patient sociodemographic characteristics on differential perfo rmance within and among plans on HEDIS measures. RESEARCH DESIGN. Using logistic regression, we modeled associations between age, sex, and residential area characteristics of health plan members and results on HEDIS measures. We then calculated the impact of adjusting for t hese associations on plan-level measures. SUBJECTS. This study included 92,232 commercially insured members with indi vidual-level HEDIS data and an additional 20,615 members whose geographic d istribution was provided. MEASURES. This study used 7 measures of screening and preventive services. RESULTS. Performance was negatively associated with percent receiving publi c assistance in the local area (6 of 7 measures), percent black (5 measures ), and percent Hispanic (2 measures) and positively associated with percent college educated (6 measures), percent urban (2 measures), and percent Asi an (1 measure) after controlling for plan and product type. These effects w ere generally consistent across plans. When measures were adjusted for thes e characteristics, rates for most plans changed by less than 5 percentage p oints. The largest change in the difference between plans ranged from 1.5% for retinal exams for people with diabetes to 20.2% for immunization of ado lescents. CONCLUSIONS. Performance on quality indicators for individual members is as sociated with sociodemographic context. Adjustment has little impact on the measured performance of most plans but a substantial impact on a few. Furt her study with more plans is required to determine the appropriateness and feasibility of adjustment.