Red blood cell life span and ‘erythropoietin resistance’

Abstract

To the Editor: We read with interest Bamgbola's review on erythropoietin (EPO) resistance in a recent issue of the Journal.1 Although the author presents a wide range of mechanisms and conditions associated with EPO resistance (including ‘accelerated turnover rate of red cells’), the integral role of red blood cell (RBC) life span deserved more explicit elaboration, in our opinion. The response to EPO, meaning the hemoglobin (Hgb) concentration achieved with a certain EPO regimen, is really a continuum rather than a binary outcome, and RBC life span (RBCLS) is a basic component of the process.2, 3 Reduction in RBCLS will necessarily entail a reduction in Hgb unless compensated for by increased RBC production rate (in dialysis patients primarily mediated by EPO and iron therapy). When RBC production cannot increase materially, regardless of increases in EPO dose, a short RBCLS becomes the limiting factor in Hgb increase, giving the impression of resistance to EPO.