Erythropoietin Resistance in Anemia of Chronic Kidney Disease

Inclusion Criteria: * prevalent patients greater than or equal to 18 years old with CKD defined as a glomerular filtration rate \< 60 cc/min Exclusion Criteria: * active GI bleeding or history of GI bleed in the prior 3 months * uncontrolled hyperparathyroidism (PTH\>500) * untreated iron deficiency (transferrin saturation \< 20% and ferritin \< 100 * overt infection * active hemolysis * hemoglobinopathies * known adverse response to erythropoietin * prior kidney transplant * aluminum toxicity