INTERFERENCE OF BLOOD LEUKOCYTES IN THE MEASUREMENTS OF IMMATURE RED-CELLS (RETICULOCYTES) BY 2 DIFFERENT (SEMI-)AUTOMATED FLOW-CYTOMETRY TECHNOLOGIES

Flow cytometrical methods have been introduced recently as an alternat ive to the enumeration of reticulocytes by microscopy. Two of these me thods have gained widespread use in haematological practice: the multi parametric flow cytometer using thiazole orange staining (Retic-Count, FACScan) and the single-application reticulocyte counter using aurami ne-O staining (R-series, Sysmex). Several studies have emphasized the excellent correlations between microscopy and these techniques. The pu rpose of our study has been to examine the specificity of these automa ted devices with regard to cells classified as 'reticulocytes' and the effect that this may have on measures of reticulocyte maturity. Our r esults indicate that the specificity of reticulocyte measurements by b oth the Sysmex R-1000/-3000 and the Retic-Count system is relatively l ow. This is due to the presence of leucocytes amongst cells classified as reticulocytes. These leucocytes display intense staining with eith er dye, leading to an erroneous estimation of RMI (thiazole orange) an d high fluorescence count (R-1000/-3000). This error is directly corre lated with the leucocyte count. The basis for reticulocyte identificat ion should be improved before automated estimation of reticulocyte mat uration can be used in clinical practice.