Evaluation of Automated Reticulocyte Counts and Their Reliability in the Presence of Howell-Jolly Bodies

Abstract

An automated reticulocyte procedure using a flow cytometer and the fluorescent dye thiazole orange was evaluated for clinical use. The mean reticulocyte count on 118 hematologically healthy adults was 1.56% (standard deviation |SD] 0.54), with virtually no difference in percentage between women and men. The mean absolute values were 68.4 × 10⁹/L (SD 24.6) and 75.7 × 10⁹/L (SD 27.2), respectively. When compared with the standard microscopic technique, the automated method showed excellent correlation (r = 0.98) and greatly improved precision (coefficient of variation [CV] 4.1%) over the manual method (CV 22.8%). Preanalytic storage of blood samples at 4 °C for up to 48 hours did not significantly affect results, nor did varying the incubation time of diluted samples from ½ to 2 hours. In a group of patients with appreciable numbers of Howell-Jolly bodies, automated reticulocyte counts were spuriously elevated. The difference between the manual and automated counts on these patients approximated the percentage of Howell-Jolly bodies observed on their Wright-Giemsa stained blood smears.