Combining health plan performance indicators into simpler composite measures.

We investigated how the Consumer Assessment of Health Plan Study (CAHPS) survey and the Health Plan Employer Data Information System (HEDIS) measures from Medicare managed care (MMC) plans could be combined into fewer summary performance scores. Four scores summarize most of the variability in these measures, representing (1) care at the doctor's office, (2) customer service and access, (3) vaccinations, and (4) clinical quality measures. These summaries are substantively interpretable, internally consistent, and describe the majority of variation among units in the performance scores analyzed.