Factors that condition the response to erythropoietin in patients on hemodialysis and their relation to mortality.

The response to erythropoietin-stimulating agents (ESA) can vary among different patients and according to the different circumstances over time within a given individual. The aim of this study was to analyze the factors that can modify the response to epoetin in patients on hemodialysis (HD) and its influence on early mortality. Prospective and observational study including 1710 patients from 119 HD units in Spain with a follow-up of 12 months. To evaluate the dose-response effect of EPO therapy, we used the erythropoietin resistance index (ERI), calculated as the weekly weight-adjusted dose of EPO divided by the hemoglobin level. Patients were stratified in three groups according to ERI: group A, ERI <5; group B, ERI=5-15; group C, ERI>15 U/kg/week/g per 100 ml. Mean ERI for the entire group was 10.2+/-7.3 U/kg/week/g per 100 ml. ERI was directly related with incident comorbidity (Charlson Index), age, female gender and low body mass index with no relationship with etiology of chronic kidney disease. Patients with antecedents of heart failure, acute infection or malignant neoplasm had significantly higher ERI than those without. Transferrin saturation index, but not serum ferritin, was inversely related with ERI. Serum levels of albumin and cholesterol were related with lower ERI, but no relation was found with normalized protein catabolic rate. Patients with a permanent catheter for HD had significant higher values of ERI than those with native fistula (P=0.012). One year survival in all three groups of patients according to ERI was 0.916 in group A, 0.877 in group B and 0.788 in group C (log-rank=20.7, P<0.001). The resistance to ESA is directly related with incident comorbidity in patients on hemodialysis and it can be interpreted as a useful marker of early mortality.