Clinical Laboratory - Hematology
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Categorization of Anemias
Normocytic: Anemia of chronic disease is common in persons who are chronically ill with underlying diseases such as inflammatory conditions like rheumatoid arthritis or hepatitis. It is typically normocytic and normochromic with low to normal serum iron and iron binding capacity low to normal, with increased % saturation, while serum ferritin is high, and reticulocyte count low.
Macrocytic: Typically from abnormal DNA synthesis (e.g. B12 or folate deficiency). They tend to be macrocytic due to a decrease in the normal number of cellular divisions during RBC differentiation by arrest in the normal growth cycle. There is normal hemoglobin synthesis, however.
Microcytic: Typically from abnormal hemoglobin synthesis (e.g. iron deficiency). They tend to be microcytic and hypochromic due to the decreases in RBC hemoglobin. Iron deficiency is diagnosed with low serum iron, high total iron binding capacity (TIBC), and low % saturation; serum ferritin low; stainable iron (i.e. Prussian Blue stain) in bone marrow decreased. It is particularly common in women of reproductive age and in children. In older adults an occult source of blood loss such as a colon cancer should be considered.
However, if there is chronic anemia in the absence of iron deficiency, particulary when the anemia has been present since childhood, a genetic cause may be present. These genetic conditions may include: hemoglobinopathies such as thalassemias with abnormal globin synthesis, and porphyrias.
The workup of chronic anemias may include a hemoglobin electrophoresis and other more esoteric labortory testing as indicated by the workup. Looking at the peripheral blood smear is important, because many congenital conditions affecting red blood cells lead to abnormal appearances.
Hemolytic anemias may be suspected when there is normocytic or mild macrocytic anemia with one or more of the following:
- Haptoglobin, serum, decreased
- Reticulocyte count, increased
- Bilirubin, serum, indirect (unconjugated), increased
- Coombs test, positive
- Lactate dehydrogenase, serum, elevated