RESUMEN
We are reporting a case of severe haemolytic anemia with cold agglutinins which combines several spurious determinations. It shows the usefulness of the new erythrocytic parameters of the XE 5000 Sysmex, specially: red blood cells with optical count (RBC-O), GR-He (intra-erythocytic hemoglobin) and R-MFV (most frequent volume). Optical red blood cells act as a substitute for red cells count instead of impedance red cells and R-MFV as a substitute for MCV (mean cell volume). The hematocrit (HCT) is corrected thanks to the following formula: HCT=(RBC-O X R- MFV)/1000. Free plasmatic hemoglobin is included in the measure of hemoglobin by the analyzer but is not available for tissue oxygenation. So, hemoglobin (HGB) has to be corrected by the means of GR- He thanks to the following formula: HGB=(GR He x RBC-O)/10.