An Automated Optoelectronic Reticulocyte Counter

Microscopic reticulocyte counting is time consuming and imprecise. A new reticulocyte counter has been developed, and the authors evaluated its utility for laboratory use. The counter, R-1000 of Sysmex-TOA Medical Electronics Company, Kobe, Japan, is based on the principles of flow cytometry. Reticulocytes are detected as fluorescent cells stained with a basic dye, auramine O, under argon-laser light. The automated count had high correlation to the manual count (r = 0.941). Linearity and reproducibility were both high. About 60 specimens were tested in one hour. Not only the reticulocyte percentage and count but also the maturity of reticulocytes was found from the intensity of the fluorescence, whether high, moderate, or slight. Normal reference values were 0.007 +/- 0.0055 (0.70 +/- 0.55%) for the reticulocytes, (4.63 +/- 1.09) X 10(9)/L for the reticulocyte count, 2.3 +/- 1.9% for highly fluorescent cells, 18.7 +/- 5.1% for moderately fluorescent cells, and 78.8 +/- 6.6% for cells with slight fluorescence. In patients with suppressed bone marrow function, such as is caused by chemotherapy, the reticulocyte fraction and count were low, and cells with slight fluorescence increased. In patients in whom bone marrow function was stimulated, such as with hemolytic anemia, the reticulocyte percentage, reticulocyte count, and highly fluorescent cells were high. Patients with chronic renal failure being treated by hemodialysis had a similar reticulocyte pattern to that in hemolytic anemia except that the reticulocyte count was decreased. Results for elderly patients were not different from those of healthy young controls. Some patients with a normal reticulocyte count and percentage had numerous highly fluorescent cells, perhaps because of hemolytic anemia not yet identified. Automated reticulocyte counting provides reliable data, so such measurement should be useful for analysis of the kinetics of red blood cells and for the study of the pathogenesis of anemia.