New red cell parameters on the Sysmex XE-2100 (TM) as potential markers offunctional iron deficiency

The ideal approach to monitor the haematological response of patients with anaemia associated with chronic renal failure during erythropoietin therapy is controversial. The reticulocyte haemoglobin content (CHr) and percentag e hypochromic red cells (% Hypo) may be used as sensitive and specific indi cators of functional iron deficiency in clinical situations with otherwise normal red cell indices. In the reticulocyte channel of a new blood cell co unter using fluorescence flow cytometry, the Sysmex XE-2100, two novel para meters are determined (RBC-Y and RET-Y) by measuring the mean value of the forward scatter histograms of red cells and reticulocytes. These values see m to equate with red cell/reticulocyte haemoglobin content. 40 normal healt hy males, 70 patients with iron deficiency (selected by indices), 90 patien ts with chronic renal failure before the start of dialysis or receiving con tinuous ambulatory peritoneal dialysis and 115 patients on long-term haemod ialysis were studied on two different blood cell counters. A soluble transf errin receptor assay and measurements of ferritin were used to assess iron status. A normal and iron-deficient range for RBC-Y and RET-Y has been defi ned and compared to the values for CHr and % Hypo. Excellent correlation be tween CHr and RET-Y (r=0.94) is obtained in all groups and reasonable corre lation with % Hypo and RBC-Y (r=0.84). The soluble transferrin receptor had Similar correlation with RET-Y and RBC-Y (r=0.68) and % Hypo (r=0.66) but less good with CHr (r=0.55). Ferritin was an unreliable indicator of functi onal iron deficiency. The two new parameters on the XE-2100 seem to indicat e functional iron deficiency, correlate with soluble transferrin receptor l evels and are acceptable alternatives to CHr and % Hypo on a routine haemat ology analyser.