Higher serum creatinine concentrations in black patients with chronic kidney disease: beyond nutritional status and body composition.

BACKGROUND AND OBJECTIVES: Serum creatinine concentrations tend to be higher in black than white individuals and people of other races or ethnicities. These differences have been assumed to be largely related to race-related differences in body composition, especially muscle mass. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In a diverse population of hemodialysis patients, we compared mean serum creatinine concentrations in black versus nonblack patients, adjusting for case mix (age, gender, diabetes, and dialysis vintage), body size (height, weight), laboratory parameters of nutritional status (albumin, predialysis blood urea nitrogen, transferrin, phosphorus, glucose), dialysis dosage (urea reduction ratio), and parameters of bioelectrical impedance (resistance and reactance), proxies for body composition.
RESULTS: Adjusted mean serum creatinine concentrations were significantly higher in black versus nonblack patients (11.7 versus 10.0 mg/dl; P < 0.0001). Black patients were roughly four-fold more likely to have a serum creatinine concentration >10 mg/dl and six-fold more likely to have a serum creatinine concentration >15 mg/dl. Higher serum creatinine concentrations were associated with a lower relative risk for death (0.93; 95% confidence interval 0.88 to 0.98 per mg/dl); the association was slightly more pronounced among nonblack patients.
CONCLUSIONS: Serum creatinine concentrations are significantly higher in black compared with nonblack hemodialysis patients; these differences are not readily explained by differences in nutritional status or body composition.