Background: The use of physician profiles in “pay for performance” initiatives depend on their reliability and accuracy.
Objectives: To evaluate whether health care delivery units (practices) can be reliably differentiated using the Health Employers Data Information System (HEDIS) performance measure.
Research Design: Simulation was used to describe the relationship between practice size (number of children with persistent asthma) and precision of practice measures to estimate performance.
Subjects: Children enrolled in 1 of the 39 practice groups from 1 of 3 managed care organizations participating in the Pediatric Asthma Care Patient Outcomes Research Team (PAC PORT).
Measures: The main outcome was reproducibility of 4 performance measures, the HEDIS measure and 3 additional measures available from automated claims data: the proportion of children with asthma related-hospitalization, emergency department visits and oral steroid dispensings for asthma.
Results: The ability to reproducibly rank a practice is dependent on the performance measure, practice size, and the reproducibility threshold chosen. Of measures evaluated, none achieved a reproducibility >85% for practice size of 50 or less. At a practice size of 100 subjects, the HEDIS measure reproducibly ranked practices 89% of the time, compared with 85% for emergency department visits and 83% for hospitalizations. Only at a practice size of 100 children with persistent asthma, was reproducibility of ranking greater than 85% with all performance measures evaluated.
Conclusions: The reliability of ranking medical practices depends on practice size. Only at the level of the health care organization can asthma measures, available within claims data, be used to rank performance reliably.