New Red Cell Parameters on the Sysmex XE-2100 as Potential Markers of Functional Iron Deficiency

The ideal approach to monitor the haematological response of patients with the anaemia associated with chronic renal failure during erythropoietin therapy is controversial. The reticulocyte haemoglobin content (CHr) and percentage hypochromic red cells (% Hypo) may be used as sensitive and specific indicators of functional iron deficiency in clinical situations with otherwise normal red cell indices. In the reticulocyte channel of a new automated haematology analyser using fluorescence flow cytometry, the Sysmex XE-2100, two novel parameters are determined (RBC-Y and RET-Y) by measuring the mean value of the forward scatter histograms of red cells and reticulocytes. These values seem to equate with red cell/reticulocyte haemoglobin content. 40 normal healthy males, 70 patients with iron deficiency (selected by indices), 90 patients with chronic renal failure before the start of dialysis or receiving continuous ambulatory peritoneal dialysis and 115 patients on longterm haemodialysis were studied on two different automated haematology analysers. A soluble transferrin 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 defined and compared to the values for CHr and % Hypo. Excellent correlation between CHr and RET-Y (r = 0.94) is obtained in all groups and reasonable correlation 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 functional iron deficiency. The two new parameters on the XE-2100 seem to indicate functional iron deficiency, correlate with soluble transferrin receptor levels and are acceptable alternatives to CHr and % Hypo on a routine haematology analyser. (Sysmex J Int 11 : 63-68, 2001)