Medication Adherence as a Measure of the Quality of Care Provided by Physicians

Abstract

Aims: To assess the extent to which medication adherence in two disease spaces – congestive heart failure (CHF) and diabetes – may serve as a measure of physician-level quality. Data and Methods: We conduct a retrospective analysis of Medicare data from 2007-2009, including Parts A (inpatient) and B (outpatient), as well as pharmacy records from Part D. For each disease, we assess the correlation between two factors: medication adherence and health outcomes, both measured at the physician-level. We control for selection bias by first regressing patient-level outcomes on a set of covariates which include co-morbid conditions, demographic attributes, and physician fixed effects. We then classify physicians into three levels of average patient medication adherence – low, medium, and high – and compare health outcomes across these groups. We conduct an additional set of comparisons adjusting for patient attributes, by using the fixed effect vectors from the initial set of regressions. Results: There is a clear relationship between average medication adherence and patient health outcomes as measured at the physician level. Within the diabetes sample, among physicians with high average adherence, and controlling for patient characteristics, 22.1 per 1,000 patients had uncontrolled diabetes, compared to 45.9 per 1,000 patients among physicians with low average adherence. Within the CHF sample, also controlling for patient characteristics, the average rate of emergency care usage for physicians with low average adherence was 16.4%, compared with 13.5% for doctors with high average adherence. Conclusions: This study establishes a physician-level correlation between improved medication adherence and improved health outcomes in the Medicare population. Our findings suggest that medication adherence may be a useful measure of physician quality, at least for chronic conditions where prescription medications are an important component of treatment.