Explaining racial disparities in outcomes after cardiac surgery: the role of hospital quality.

IMPORTANCE: Racial disparities in mortality rates after coronary artery bypass graft (CABG) surgery are well established. We have yet to fully understand how care at high-mortality, low-quality hospitals contributes to racial disparities in surgical outcomes. OBJECTIVE: To determine the effects of hospital quality on racial disparities in mortality rates after CABG surgery. DESIGN, SETTING, AND PARTICIPANTS: The national Medicare database (2007-2008) was used to identify 173,925 patients undergoing CABG surgery in US hospitals. MAIN OUTCOMES AND MEASURES: Our primary measure of quality was the risk-adjusted mortality rate for each hospital. Logistic regression was used to determine the relationship between race and mortality rates, accounting for patient characteristics, socioeconomic status, and hospital quality. RESULTS: Nonwhite patients had 33% higher risk-adjusted mortality rates after CABG surgery than white patients (odds ratio [OR], 1.33; 95% CI, 1.23-1.45). In hospitals treating the highest proportion of nonwhite patients (>17.7%), the mortality was 4.8% in nonwhite and 3.8% in white patients. When assessed independently, differences in hospital quality explained 35% of the observed disparity in mortality rates (OR, 1.22; 95% CI, 1.12-1.34). We were able to explain 53% of the observed disparity after adjusting for differences in socioeconomic status and hospital quality. However, even after these factors were taken into account, nonwhite patients had a 16% higher mortality (OR, 1.16; 95% CI, 1.05-1.27). CONCLUSIONS AND RELEVANCE: Hospital quality contributes significantly to racial disparities in outcomes after CABG surgery. However, a significant fraction of this racial disparity remains unexplained. Efforts to decrease racial disparities in health care should focus on underperforming centers of care treating disproportionately high numbers of nonwhite patients.