[Automated hematology analysers and spurious counts Part 2. Leukocyte count and differential]. / Anomalies et erreurs de détermination de l'hémogramme avec les automates d'hématologie cellulaire Partie 2. Numération et formule leucocytaires.

Using hematology analysers, white blood cell (WBC) counts and differentials (either three or five parameters) may be ascertained after Red Blood Cell (RBC) lysis and analysis using either impedance and/or optical (laser) technology. Cells or particles not destroyed by lytic agents are enumerated as WBC: abnormal particles may be observed on WBC differential scattergrams, if performed, appearing as a variable number of dots, which location may help to ascertain the nature of the abnormality. Spuriously low WBC counts are rare, mainly related to agglutination in the presence of ethylenediamine tetra-acetic acid. Cryoglobulins, lipids, insufficiently lysed RBC, erythroblasts and platelet aggregates are common situations increasing WBC counts. So far, many current high performance analysers clearly identify and enumerate erythroblasts now. In normal patients and in reactive disorders automated differential provides true and accurate results. However, failure to enumerate accurately basophilic granulocytes and monocytes is not uncommon. Using myeloperoxidase cytochemistry to ascertain differential may lead to slide review if the enzyme expression is low or absent. Low number of abnormal cells (blasts, lymphoma cells, dysplastic granulocytes) may be missed, more frequently if leukopenia is present. In many but not all instances flagging and/or an abnormal WBC differential scattergram will alert the operator. Although these flags are sensitive enough to allow the identification of several spurious counts, only the most sophisticated analysers have optimal flagging, whereas more simple ones, especially those without a WBC differential scattergram, do not demonstrate the same sensitivity for the detection of abnormal results.

[Automated hematology analysers and spurious counts Part 3. Haemoglobin, red blood cells, cell count and indices, reticulocytes]. / Anomalies et erreurs de détermination de l'hémogramme avec les automates d'hématologie cellulaire Partie 3. Hémoglobine, hématies, indices érythrocytaires, réticulocytes.

Several situations lead to abnormal haemoglobin measurement or to abnormal red blood cells (RBC) counts, including hyperlipemias, agglutinins and cryoglobulins, haemolysis, or elevated white blood cells (WBC) counts. Mean (red) cell volume may be also subject to spurious determination, because of agglutinins (mainly cold), high blood glucose level, natremia, anticoagulants in excess and at times technological considerations. Abnormality related to one measured parameter eventually leads to abnormal calculated RBC indices: mean cell haemoglobin content is certainly the most important RBC parameter to consider, maybe as important as flags generated by the haematology analysers (HA) themselves. In many circumstances, several of the measured parameters from cell blood counts (CBC) may be altered, and the discovery of a spurious change on one parameter frequently means that the validity of other parameters should be considered. Sensitive flags allow now the identification of several spurious counts, but only the most sophisticated HA have optimal flagging, and simpler ones, especially those without any WBC differential scattergram, do not share the same capacity to detect abnormal results. Reticulocytes are integrated into the CBC in many HA, and several situations may lead to abnormal counts, including abnormal gating, interference with intraerythrocytic particles, erythroblastosis or high WBC counts.