Approach to Anemia

• The presence of sickle hemoglobin (HbS) shift the curve to the right (oxygen is given up more easily) whereas fetal hemoglobin (HbF) – which is unable to bind 2,3‐DPG – and certain rare abnormal hemoglobins associated with polycythemia shift the curve to the left because they give up O2 less readily than normal.

• Erythropoiesis is not entirely efficient because approximately 10–15% of developing erythroblasts die within the marrow without producing mature cells. This is termed ineffective erythropoiesis and it is substantially increased in a number of chronic anemias.
• The serum unconjugated bilirubin (derived from breaking down hemoglobin) and lactate dehydrogenase (derived from breaking down cells) are usually raised when ineffective erythropoiesis is marked. The reticulocyte count is low in relation to the degree of anemia and to the proportion of erythroblasts in the marrow.
• Effective erythropoiesis is assessed by the reticulocyte count. After an acute major hemorrhage there is an erythropoietin response in 6 hours, the reticulocyte count rises within 2–3 days, reaches a maximum in 6–10 days and remains raised until the hemoglobin returns to the normal level.
• When the reticulocyte count is reported as a percentage, it needs to be adjusted for the total number of RBCs present. This correction can be made by multiplying the reticulocyte count by the patient's hematocrit divided by an age-and sex-appropriate normal hematocrit. No such correction is necessary when the reticulocyte count is reported as an absolute number or when it is converted to an absolute number by multiplying the percentage by the RBC number (in RBC/µL). In the absence of anemia, the normal absolute reticulocyte count is between 25,000 and 75,000/µL. In the presence of anemia, an absolute reticulocyte count of less than 75,000/µL is indicative of a hypoproliferative process, and an absolute reticulocyte count of greater than 100,000/µL is indicative of hemolysis or an appropriate erythropoietic response to blood loss

This is normal data from a complete blood count as performed on an automated instrument, including an automated WBC differential count.

Iron deficiency anemia

• Note the low hemoglobin.
• Microcytosis is indicated by the low MCV (mean corpuscular volume).
• Hypochromia correlates here with the low MCH (mean corpuscular hemoglobin).

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Megaloblastic anemia

• A markedly increased MCV typical for megaloblastic anemia.
• The MCV can be mildly increased in persons recovering from blood loss or hemolytic anemia, because the newly released RBC's, the reticulocytes, are increased in size over normal RBC's, which decrease in size slightly with aging.

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Microangiopathic hemolytic anemia

• A markedly increased RDW (red cell distribution width) due to the marked variation in size and shape of the RBC population.

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Spherocytosis

• A condition in which the RBC's are small and round (rather than the normal biconcave appearance) with increased hemoglobin content. This is indicated here by the increase MCHC (mean corpuscular hemoglobin concentration).
• There is a rare condition known as hereditary spherocytosis.
• Also, RBC's in the condition of autoimmune hemolytic anemia can also appear similarly.

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Transfusion

• Transfusion accounts for the dual RBC population as seen in the graph at the lower left.
• A reticulocytosis in response to anemia has also increased the MCV.

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Iron Metabolism