**11. Summary**

The final stage of RBC differentiation occurs in the peripheral blood. The reticulocytes that are released by the bone marrow still contain RNA. On the way of maturation reticulocytes gradually lose their rough endoplasmic reticulum and mitochondria to become mature RBC after about 3–4 days in the peripheral blood. Since the number and characteristics of the reticulocytes in the peripheral blood gives insight about the activity of the bone marrow, reticulocyte counting has become fundamental part of the hematopoietic evaluation now-a-days. Circulating reticulocytes decrease in patients with impaired bone marrow function, and increase in cases of hemolysis with normal bone marrow activity. Reticulocyte enumeration by light microscopy, with the use of a supravital dye (*viz*. NMB), which binds to the RNA in the reticulocyte still remains the standard method for RC. However, the accuracy and precision of this assay are greatly compromised by its subjective nature. In contrast, automated techniques of reticulocyte enumeration are more precise, accurate, objective, and cost-effective. A variety of RNA-specific fluorescent dyes have been utilized for automated reticulocyte enumeration, and some hematology analyzers utilize optical light scatter analysis to perform reticulocyte analysis on specimens stained with NMB or other dyes. In addition to relative and absolute reticulocyte counts, automated techniques provide information regarding the age distribution of reticulocytes in form of the RMI, IRF, CHr. There is extensive evidence that these parameters are useful in the accurate classification of anemia patients, and monitoring patients receiving EPO or recovering from chemotherapy or bone marrow transplantation. The recent trend to incorporate reticulocyte analysis into the routine hematology analyzer has made automated reticulocyte analysis increasingly such common that, perhaps in recent future, the manual reticulocyte count will become an obsolete technique.
