[Clinical usefulness of reticulocyte hemoglobin equivalent (RET-He) in patients at the pre-dialysis stage and in patients on peritoneal dialysis].

BACKGROUND: Evaluation of the iron status of patients with renal anemia provides information essential to prescribing adequate rHuEPO therapy. Cellular iron status can be determined by the recently available method of measuring the reticulocyte hemoglobin equivalent (RET-He). We previously showed that RET-He values were correlated with conventional parameters and with a direct marker of the reticulocyte hemoglobin (CHr) content of hemodialysis patients. We attempted to utilize the measurements of RET-He levels of non-dialyzed patients and the iron status of peritoneal dialysis (PD) patients. METHODS: Iron deficiency was defined on the basis of the TSAT (< 20 %) and ferritin (< 100 ng/mL) levels. RET-He levels and conventional red blood cell parameters were measured with a Sysmex XE-2100 automated blood cell counter. CHr was measured with an ADVIA120 autoanalyzer. The serum hepcidin levels of PD patients were measured by mass-spectrometry. RESULTS: The mean RET-He value was 32.0 pg in the non-dialysis group and 32.5 pg in the PD group, and a correlation was found between the RET-He and TSAT values, but not the ferritin values in both groups. The serum hepcidin level was 49.8 pg in the PD group and there was a positive correlation between their hepcidin and ferritin values. Receiver operating characteristic analysis yielded a cut-off value of RET-He in the non-dialysis group (31.0 pg) and the PD group (32.7 pg). The RET-He values of PD patients who were switched from epoetin beta to darbepoetin alfa responded more rapidly than TSAT or ferritin values. CONCLUSION: RET-He is a new parameter, whose values are equivalent to CHr, and can be easily measured with a widely available and popular blood cell counter. Reticulocyte hemoglobin is an indispensable marker of iron status for chronic kidney disease patients. Moreover, reticulocyte hemoglobin is likely to provide useful information regarding the need for iron supplementation in patients being treated with an ESA.