Slightly immature, non-nucleated red blood cells (reticulocyte stage) appear bluish-gray in Wright-stained smears due to the presence of residual ribonucleic acid (RNA).
These cells are called polychromatophilic cells . Polychromatophilic cells are often larger than mature red cells and can be distinguished from macrocytes by their distinctive blue-gray color.
This condition is also called polychromasia .
In the image, the cells are slightly bluish-gray in color and are examples of polychromatophilic red blood cells. A higher number of these cells (averaging 2 or more per oil immersion field) indicates increased production of red blood cells by the bone marrow.
Under normal conditions, these young red blood cells remain in the bone marrow for a day or two before being released into the bloodstream. However, when the bone marrow is stressed due to blood loss or other conditions, these cells are released prematurely into the blood.
If stained with a supravital stain, they would be identified as reticulocytes.
Late maturing red blood cells (arrow), these cells are larger in diameter than mature red blood cells, all slightly basophilic in color.
Polychromatophilic red blood cells are seen after staining with the Romanowsky stain (Wright-Giemsa, Diff-Quik®).
The reticulocyte is the same cell but is seen after staining with new methylene blue. In the case of anemia, the presence of polychromatophilic red blood cells in the blood smear is an indicator of a certain level of regeneration.
Too many reticulocytes are seen more often when the bone marrow needs to make more red blood cells due to a certain condition, such as hemolytic anemia.
General approach to anemias
Anemia is present in adults if the hematocrit is less than 41% (hemoglobin less than 13.6 g / dL [135 g / L]) in men or less than 36% (hemoglobin less than 12 g / dL [120 g / L / L]) in women. Congenital anemia is suggested by the patient’s personal and family history.
The most common cause of anemia is iron deficiency. A poor diet can lead to folic acid deficiency and contribute to iron deficiency, but bleeding is the most common cause of iron deficiency in adults.
Physical examination shows paleness. It is important to pay attention to the physical signs of primary hematologic diseases (lymphadenopathy; hepatosplenomegaly; or bony tenderness, especially in the sternum or anterior tibia). Mucosal changes, such as a smooth tongue, suggest megaloblastic anemia.
Anemias are classified according to their pathophysiological basis, that is, if they are related to a decreased production (relative or absolute reticulocytopenia) or to a greater production due to the accelerated loss of red blood cells (reticulocytosis), and according to the red blood cells.
A reticulocytosis occurs in one of three pathophysiologic states: acute blood loss, recent replacement of a missing erythropoietic nutrient, or reduced red blood cell survival (ie, hemolysis).
A severely microcytic anemia (mean corpuscular volume [MCV] less than 70 fL) is due to iron deficiency or thalassemia, while a severe macrocytic anemia (MCV greater than 120 fL) is almost always due to megaloblastic anemia or cold agglutinins in the blood tested at room temperature.
In general, a bone marrow biopsy is needed to complete the anemia evaluation when laboratory evaluation does not reveal an etiology, when additional cytopenias are present, or when an underlying primary or secondary bone marrow process is suspected.
Reticulocytes provide an assessment of the bone marrow’s response to anemia. The reticulocyte release rate from the bone marrow indicates the erythroid component of the bone marrow. A reticulocyte stain measures aggregates of residual ribosomes and mitochondria that form clumped granular material called the reticulum.
Reticulocytes appear as polychromatophilic cells seen on a film of Wright or Wright-Giemsa stained blood.
The fresh methylene blue or bright cresyl blue is mixed with several drops of blood and incubated for 10 minutes in a tube before making a blood film.
Reticulocytes are counted out of 1000 erythrocytes on a blood film and are expressed as a percentage of erythrocytes. In anemia, the number will be altered, so the number of reticulocytes per µl is calculated as red blood cells / µl ×% reticulocytes.