Does the survival advantage of nonwhite dialysis patients persist after case mix adjustment?

PURPOSE: Nonwhite dialysis patients survive longer than white patients; how ever, their clinical characteristics differ. We examined whether case mix d ifferences explain the apparent survival advantage of nonwhite dialysis pat ients. SUBJECTS AND METHODS: We performed a prospective cohort study using data fr om the US Renal Data System Case Mix Severity Study that included 4,797 ran domly selected dialysis patients 20 years of age and older who were followe d up for up to 6 years. Demographic, comorbidity, laboratory, nutritional, and functional status data were obtained. Multivariable proportional hazard s models adjusted for case mix differences between nonwhite and white dialy sis patients. Additional analyses examined the effects of differences in tr ansplantation rates, withdrawal from dialysis rates, and treatment modality selection. RESULTS: Unadjusted survival rates of black, Native American, and Asian or Pacific Islander dialysis patients were similar, and better than that for w hite dialysis patients. Relative to whites, the unadjusted relative risk (R R) for mortality among nonwhite patients was 0.64 (95% confidence interval [CI]: 0.58 to 0.70). Adjustment for case mix reduced, but did not eliminate , the survival advantage associated with nonwhite race (RR = 0.78, CI: 0.71 to 0.86). Adjustment for differences in transplantation rates (RR = 0.83, CI: 0.75 to 0.91), withdrawal from dialysis rates (RR = 0.81, CI: 0.73 to 0 .90), and initial treatment modality (RR = 0.79, CI: 0.71 to 0.87) did nor explain the lower mortality among nonwhites. CONCLUSIONS: A survival advantage for nonwhite dialysis patients persists a fter case mix adjustment. Future studies should explore additional physiolo gic and socioeconomic factors that might explain this difference. (C) 1999 by Excerpta Medica, Inc.