Background: In a simulation based on a pharmacokinetic model we demonstrated that increasing the erythropoiesis stimulating agents (ESAs) half-life or shortening their administration interval decreases hemoglobin variability. The benefit of reducing the administration interval was however lessened by the variability induced by more frequent dosage adjustments. The purpose of this study was to analyze the reticulocyte and hemoglobin kinetics under different ESAs and administration intervals in a collective of chronic hemodialysis patients.

Methods: The study was designed as an open-label, randomized, four-period cross-over investigation, including 30 patients under chronic hemodialysis at the regional hospital of Locarno (Switzerland) in September 2009 and lasting 2 years. Four treatment strategies (C.E.R.A. every 4 weeks Q4W and every 2 weeks Q2W, Darbepoetin alfa Q4W and Q2W) were compared with each other. The mean square successive difference of hemoglobin, reticulocyte count and ESAs dose was used to quantify variability. We distinguished a short- and a long-term variability based respectively on the weekly and monthly successive difference.

Inclusion Criteria:

• chronic patients aged 18 years or older, undergoing dialysis 3 times a week for at least 8 weeks before screening, necessitating continuous subcutaneous treatment with weekly Darbepoetin alfa or Erythropoietin beta to maintain hemoglobin (Hb) targets

Exclusion Criteria:

• pregnancy; not respecting the inclusion criteria