Revisiting survival differences by race and ethnicity among hemodialysis patients: the Dialysis Outcomes and Practice Patterns Study.

Hemodialysis (HD) patients who are identified as belonging to racial or ethnic minority groups have longer survival than non-Hispanic white HD patients. This study sought to determine to what extent this survival difference is explained by comprehensive adjustment for measurable case-mix and treatment characteristics. A cohort analysis was conducted among 6677 patients between 1996 and 2001 in the American arm of the first phase of the Dialysis Outcomes and Practice Patterns Study, a prospective observational study. Using multivariable proportional hazards analysis, all-cause mortality by racial/ethnic category was compared before and after adjustment for other patient-level variables that are associated with mortality. Factors that influence the statistical associations of race/ethnicity with mortality were explored. The statistically significant (P < 0.001) associations of racial/ethnic minority categories with lower mortality in unadjusted analyses were attenuated or lost in the multivariable model. Compared with non-Hispanic white patients, the adjusted hazard ratio (HR) (95% confidence interval [CI]) for mortality was 0.86 (0.72 to 1.03) for Hispanic patients; among non-Hispanic patients, the HR (95% CI) were 0.97 (0.85 to 1.11) for black patients, 0.82 (0.56 to 1.20) for Asian patients, 0.95 (0.52 to 1.73) for Native American patients, and 0.95 (0.60 to 1.50) for patients of other races (overall P = 0.66). The survival advantages for racial/ethnic minority categories were explained most notably by the combined influence of unbalanced distributions of numerous demographic, morbidity, nutritional, and laboratory variables. The associations of race/ethnicity with survival varied little by duration of ESRD and were not influenced substantially by different rates of kidney transplantation among patients who were on HD. The survival advantages for racial and ethnic minority groups on HD are explained largely by measurable case-mix and treatment characteristics. Individual racial minority group or Hispanic patients should not be expected to survive longer on HD than non-Hispanic white patients with similar clinical attributes.