Reticulocytes: Biological variations and reference limits

: The reticulocyte count is a good index of erythropoietic activity. Automated methods, mainly flow cytometry, have made the counting easier, more accurate and reproducible. The data presented describe the counting of reticulocytes in 1219 apparently healthy subjects of both sexes who came for a periodic health examination. Their ages varied from 4 to over 60 years. The reticulocytes were counted with a flow cytometer (Sysmex R-3000) with Auramine-O as fluorochrome. There was no statistical difference between boys and girls aged 4–19 years. However, the reticulocyte count was significantly higher in men than in women over 20 years of age. The reticulocyte count was affected neither by the menstrual cycle in girls at puberty, nor by oral contraceptives and the menopause in women. No effect of moderate smoking was observed in either sex. Reference limits of the reticulocyte counts (percentage and absolute value) according to age and sex and of the three types of reticulocytes are provided.