METHODOLOGY-DEPENDENT VARIATIONS IN RETICULOCYTE COUNTS USING A MANUAL AND 2 DIFFERENT FLOW CYTOMETRIC PROCEDURES

This paper describes a comparison between the microscopic brilliant cr esyl blue and the flow cytometric thiazol orange (FACScan) and auramin e O (Sysmex) methods for enumeration of reticulocytes. The mean intra- assay coefficients of variation for the microscopic, FACScan and Sysme x methods were established to be 33, 9 and 5% respectively. A rather p oor correlation was observed between the microscopic count and both fl ow cytometric methods (FACScan r = 0.61; Sysmex r = 0.57). However, th e correlation between the flow cytometric methods was satisfactory (r = 0.79). Reference ranges for the reticulocyte count, corresponding wi th the 2.5th and 97.5th percentile, were determined for the microscopi c (8-30 parts per thousand), FACScan (11-27 parts per thousand) and Sy smex (8-18 parts per thousand) methods. Sysmex R-3000 methodology defi nitely revealed the lowest and narrowest reference range. In conclusio n, because of higher reproducibility, flow cytometric analysis of reti culocytes is an attractive alternative procedure for the microscopic e numeration method.