Erythrocyte and reticulocyte indices in iron deficiency in chronic kidney disease: comparison of two methods

Objective. Anaemia is a common complication of chronic kidney disease (CKD), particularly in dialysis patients. The recent European guidelines for anaemia treatment in CKD indicate the percentage of hypochromic red cells (%HYPO) and reticulocyte haemoglobin content (CHr) calculated by Siemens ADVIA haematology analysers as a useful tool indicating iron deficiency. The aim of this study was to evaluate the agreement between CHr and %HYPO parameters and the reticulocyte haemoglobin equivalent (RET‐He) and red blood cell haemoglobin equivalent (RBC‐He) calculated by the Sysmex XE‐2100 haematology analyser in a cohort of 200 dialysis patients referred to the Nephrology Unit of our hospital. Furthermore, we evaluated a new index, the DF‐Hypo XE, obtained from haemoglobin (Hb), haematocrit (Hct) and RET‐He, provided by the Sysmex XE‐2100, as a new potential marker of %HYPO in dialysed patients. Material and methods. Blood samples collected in EDTA anticoagulant from 200 CKD patients receiving erythropoietin and iron to maintain haemoglobin level between 10 and 12?mg/dL were analysed on both the Siemens ADVIA 2120 and the Sysmex XE‐2100 within 2?h of collection. Results. There was good correlation between CHr and RET‐He (r = 0.88; p<0.0001), %HYPO and DF‐Hypo XE (r = 0.89; p<0.0001) and between RBC‐He and CH (r = 0.96; p<0.0001), but there was a lower correlation, even though statistically significant, between RBC‐He and %HYPO (r = ?0.59; p<0.0001). The Altman‐Bland analysis showed a very good level of agreement between CHr and RET‐He (mean bias = 1.04?pg), %HYPO and DF‐Hypo XE (mean bias = 1.73). Using a cut‐off value of 29.4?pg for the RET‐He and of 10.2 for the DF‐Hypo XE, 15 out 17 patients with a CHr <29.0?pg and 9 out 11 patients with a %Hypo <10.0% were respectively correctly identified. Conclusions. Our study shows good correlation and agreement between CHr and RET‐He and between %HYPO and DF‐Hypo XE in evaluating CKD patients needing iron support.