Background: Little information is available regarding variations in diabetes mellitus (DM) outcomes by race at the level of individual physicians.
Methods: We identified 90 primary physicians caring for at least 5 white and 5 black adults with DM across 13 ambulatory sites and calculated rates of ideal control of hemoglobin A(1c) (HbA(1c)) (<7.0%), low-density lipoprotein cholesterol (LDL-C) (<100 mg/dL), and blood pressure (<130/80 mm Hg). We fitted hierarchical linear regression models to measure the contributions to racial disparities of patient sociodemographic factors, comorbidities, and physician effects. Physician effects modeled the extent to which black patients achieved lower control rates than white patients within the same physician's panel ("within-physician" effect) vs the extent to which black patients were more likely than white patients to receive care from physicians achieving lower overall control rates ("between-physician" effect).
Results: White patients (N = 4556) were significantly more likely than black patients (N = 2258) to achieve control of HbA(1c) (47% vs 39%), LDL-C (57% vs 45%), and blood pressure (30% vs 24%; P < .001 for all comparisons). Patient sociodemographic factors explained 13% to 38% of the racial differences in these measures, whereas within-physician effects accounted for 66% to 75% of the differences. Physician-level variation in disparities was not associated with either individual physicians' overall performance or their number of black patients with DM.
Conclusions: Racial differences in DM outcomes are primarily related to patients' characteristics and within-physician effects, wherein individual physicians achieve less favorable outcomes among their black patients than their white patients. Efforts to eliminate these disparities, including race-stratified performance reports and programs to enhance care for minority patients, should be addressed to all physicians.