Reticulocyte
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Reticulocytes are immature red blood cells, typically comprising about 1% of the red cells in the human body. Reticulocytes develop and mature in the red bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells. Like mature red blood cells, reticulocytes do not have a cell nucleus. They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA that becomes visible under a microscope with certain stains.
Reticulocytes appear slightly bluer than other red cells when looked at with the normal Romanowsky stain. Reticulocytes are also slightly larger, which can be picked up as a high MCV (mean corpuscular volume) with a full blood count done by machine.
[edit] Reticulocyte count
The reticulocyte count is the percentage of circulating red blood cells that are in the reticulocyte stage.
To accurately measure reticulocyte counts, automated counters that use lasers mark cell samples with fluorescent dye that marks RNA and DNA. This distinguishes reticulocytes as the middle ground of dye response to laser light, between red blood cells (which have neither RNA nor DNA) and lymphocytes (which have a large amount of DNA, unlike reticulocytes).[1]
The normal range of values for reticulocytes in the blood depends on the clinical situation and the lab, but broadly speaking is 0.5% to 1.5%. However, if a person is anemic, their reticulocyte percentage should be higher. Calculating the reticulocyte production index is an important step in understanding whether the reticulocyte count is appropriate or inappropriate to the situation, which is often a more important question than whether the percentage is in the normal range. The number of reticulocytes is a good indicator of red bone marrow activity; thus, the reticulocyte count and the reticulocyte production index that can be calculated from it can be used to monitor the progress of treatment for anaemia. The specimen requirement for a reticulocyte count is EDTA anti-coagulated whole blood, which is generally a lavender-top test tube.
Reticulocytes increase in number and percentage when there is increased production of red blood cells such as in a haemolytic anaemia or sickle cell anemia. The increase in reticulocytes is called reticulocytosis.
Abnormally low numbers of reticulocytes can be attributed to chemotherapy, aplastic anemia, pernicious anemia, bone marrow malignancies, problems of erythropoietin production, or other causes of anaemia due to poor RBC production.
