[Resistance index to epoetin alpha and to darbepoetin-alpha in chronic hemodialysis patients: a cohort study]. / Estudio de dos cohortes de pacientes para evaluar el índice de resistencia a epoetina alfa y a darbepoetin alfa en pacientes en hemodiálisis crónica.

ABSTRACT

The effectiveness of the erythropoietic response can be evaluated using the resistance index (RI) to erythropoietic agents (EA) that measures the relationship between the dose administered and the hemoglobin levels attained. In a hemodialysis population, the RI is associated with several clinical and biochemical parameters, such as albumin levels, C-reactive protein (CRP), body mass index (BMI) and Kt/V. This index therefore reflects an important group of parameters that indicate comorbidities and measures the effectiveness of the treatment received. A substantial proportion of chronic hemodialysis patients show a relative resistance to human recombinant erythropoietin (rHuEPO) and require high doses to reach hemoglobin levels above 11 g/dl. Darbepoetin alpha is a new erythropoietic agent with a longer half-life than rHuEPO and greater biological activity in vivo. Furthermore, it remains at clinically effective plasma levels for much longer than rHuEPO. This study evaluated the effect on RI of switching from epoetin alpha to darbepoetin alpha in hemodialysis patients requiring i.v. rHuEPO at either high ( >10,000 UI/w) or low ( <4,000 UI/w) doses, compared to a control group receiving epoetin alpha. Unlike the control group, both groups of patients who switched to darbepoetin alpha showed a reduction in RI and a progressive reduction in the dose required of darbepoetin alpha with respect to the equivalent dose at treatment conversion. In the group requiring high doses, darbepoetin alpha RI (DRI) at week 24 was a significant 23.9% lower than epoetin alpha RI (ERI) at conversion (week 0) (p <0.01). In the group requiring low doses, DRI at week 24 was 13.4% lower than the ERI at conversion (p = NS). In both control groups, ERI at week 24 was higher than ERI at week 0. All groups showed stable hemoglobin levels across the study, with mean levels between 11.5 and 13.3 g/dl. CRP at week 24 was significantly related to albumin levels (p <0.001). In conclusion, switching hemodialysis patients from epoetin alpha to darbepoetin alpha was associated with a significant improvement in RI in the group of patients with high doses of EA, which we consider to be an important indicator of the effectiveness and quality of the treatment administered.