The prevalence of anemia in patients with chronic kidney disease.

OBJECTIVE: Anemia is a complication of chronic kidney disease and may contribute to adverse clinical outcomes. Early identification and treatment of anemia may improve cardiovascular morbidity and mortality. No large-scale population data are available specifically for patients with chronic kidney disease regarding prevalence of anemia, subpopulations at risk, and relationships between anemia and kidney function. This study was undertaken to address these questions in patients with chronic kidney disease, and investigate the relationship between anemia and glomerular filtration rate.

RESEARCH DESIGN AND METHODS: Large-scale, cross-sectional, US multicenter survey; 5222 patients (mean age, 68.2 years; 46.6% male); 237 physician practices. Eligible patients: > or = 18 years of age; serum creatinine: 1.5 mg/dL-6.0 mg/dL (females), 2.0 mg/dL-6.0 mg/dL (males).

MAIN OUTCOME MEASURES: Primary study end point: prevalence and severity of anemia (hemoglobin < or = 12 g/dL). Data further stratified by hemoglobin (< or = 12 g/dL, < or = 10 g/dL).

RESULTS: Primary etiologies of chronic kidney disease (5222 evaluable patients): diabetes (49.5%); hypertension (33.0%). Glomerular filtration rate: < 60 mL/min/1.73 m2 for 97.7% of evaluable patients. Mean +/- SD serum creatinine level: 2.2 mg/dL +/- 0.9 mg/dL; 2.5 mg/dL +/- 1.0 mg/dL for males, 2.0 mg/dL +/- 0.8 mg/dL for females. Mean +/- SD hemoglobin: 12.2 g/dL +/- 1.6 g/dL (47.7% had hemoglobin < or = 12 g/dL; 8.9% had hemoglobin < or = 10 g/dL). Prevalence of anemia was strongly associated with declining glomerular filtration rate. Percentage of patients with hemoglobin < or = 12 g/dL increased from 26.7% to 75.5% when glomerular filtration rate decreased from > or = 60 mL/min/1.73 m2 to < 15 mL/min/1.73 m2. Prevalence of hemoglobin < or = 10 g/dL increased substantially from 5.2% to 27.2% when glomerular filtration rate diminished from > or = 60 mL/min/1.73 m2 to < 15 mL/min/1.73 m2. After controlling for other patient characteristics associated with increased prevalence of anemia, the prevalence odds ratio for hemoglobin < or = 10 g/dL was 0.54 (0.49-0.60) and for hemoglobin < or = 12 g/dL was 0.68 (0.65-0.72), with each 10-mL/min/1.73 m2 increase in glomerular filtration rate. Predictors of anemia: diabetes, female sex, and race/ethnicity.

CONCLUSIONS: Anemia was present in 47.7% of 5222 predialysis patients with chronic kidney disease. Prevalence of anemia increased as kidney function decreased. Certain subgroups are at increased risk for anemia.