Does the survival advantage of nonwhite dialysis patients persist after case mix adjustment?
OBJECTIVE
Nonwhite dialysis patients survive longer than white patients; however, their clinical characteristics differ. We examined whether case mix differences explain the apparent survival advantage of nonwhite dialysis patients.


METHODS
We performed a prospective cohort study using data from the US Renal Data System Case Mix Severity Study that included 4,797 randomly selected dialysis patients 20 years of age and older who were followed up for up to 6 years. Demographic, comorbidity, laboratory, nutritional, and functional status data were obtained. Multivariable proportional hazards models adjusted for case mix differences between nonwhite and white dialysis patients. Additional analyses examined the effects of differences in transplantation 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 white dialysis patients. Relative to whites, the unadjusted relative risk (RR) 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 not explain the lower mortality among nonwhites.


CONCLUSIONS
A survival advantage for nonwhite dialysis patients persists after case mix adjustment. Future studies should explore additional physiologic and socioeconomic factors that might explain this difference.
Mesler
D E
DE
Evans Department of Medicine, Boston Medical Center, MA 02118, USA.
McCarthy
E P
EP
Byrne-Logan
S
S
Ash
A S
AS
Moskowitz
M A
MA
D000328:Adult; D000368:Aged; D003953:Diagnosis-Related Groups; D005260:Female; D006801:Humans; D008297:Male; D006278:Medicare; D008875:Middle Aged; D008913:Minority Groups / Q000706:statistics & numerical data*; D015233:Models, Statistical; D006435:Renal Dialysis / Q000401:mortality*; D012306:Risk; D012307:Risk Factors; D012720:Severity of Illness Index; D015996:Survival Rate; D014481:United States / Q000453:epidemiology