The required dose of erythropoietin during renal anaemia treatment is related to the degree of impairment in erythrocyte deformability.

BACKGROUND Renal anaemia is rapidly corrected by recombinant human erythropoietin (rHuEpo) therapy, but the dose required varies greatly. Since impaired erythrocyte deformability may be one factor contributing to the development of renal anaemia, the interrelationship between that variable and the rHuEpo requirement was examined. METHODS Twenty-five patients treated with hemodialysis and rHuEpo for at least 6 months were included in the study. The Hb value had been stable and the rHuEpo dose unchanged the last two months. Using a rotational viscometer, the fluidity of erythrocytes, separated from plasma and re-suspended in isotonic buffered saline to a standardized haematocrit, was taken as a measure of erythrocyte deformability. RESULTS The average weekly dose of s.c. epoetin alpha was 186 +/- 93 U/kg body weight (range 56-370). The dose was correlated to the reticulocyte fraction (R = 0.69, P = 0.0001). When the rHuEpo dose was used as dependent variable and blood haemoglobin concentration, serum (S) albumin, S ferritin, S aluminium, S PTH, S urea, Kt/V/week, erythrocyte fluidity, and plasma viscosity were used as independent variables in a stepwise multiple regression analysis, only erythrocyte fluidity remained significantly negatively correlated to the rHuEpo dose (R = 0.5, P = 0.01). Despite a tendency towards higher doses of rHuEpo in patients with a C-reactive protein concentration exceeding 20 mg/l, the Hb was lower in these patients. CONCLUSIONS We conclude that the interindividual differences in bone marrow response to rHuEpo were small in these patients. Impaired erythrocyte deformability and inflammation seem to be factors associated with increased rHuEpo requirement.