A common type of anemia is called microcytic anemia. It is characterized by the small size of the red blood cell. In order to be diagnosed with microcytic anemia, the red blood cell has to have a mean corpuscular volume (MCV) of less than 80 fL, with 80-100 fL being the normal mean corpuscular volume.
Microcytic anemia can be further divided into various subtypes. These subtypes include:
- Iron deficiency anemia
- Sideroblastic anemia
Iron Deficiency Anemia
In Iron deficiency anemia, there is a low level of iron within the blood’s serum. It is also characterized by a low level of ferritin or iron in its elemental state. The difference between iron deficiency anemia, and the other subtypes of microcytic anemia is the Total Iron Binding Capacity (TIBC). The TIBC is high in iron deficiency anemia, but low in all the other subtypes. This is one way to distinguish if the anemia is due to a lack of iron.
If a laboratory technician were to view the red blood cells of someone with iron deficiency anemia, they would see red blood cells with pale centers. It would resemble a donut, and hence they are called “donut cells."
Sideroblastic Anemia is the second subtype of microcytic anemia. It is different from iron deficiency anemia because the cells have the classic sideroblasts inside of them. Someone with sideroblastic anemia would not have a low amount of ferritin, but rather tests would show a high ferritin level. However, there is still the same low level of iron in the blood’s serum, but with a low or a normal level of the TIBC. Sideroblastic anemia usually results from ingestion or exposure to lead, or medication such as chloramphenicol.
The third type of anemia is Thalassemia, which will be discussed in the next part of this article series.
Macrocytic anemia results from a deficiency of folate or Vitamin B12. It can also result form hemolytic anemia in which the red blood cells are destroyed. Certain drugs such as barbiturates can also cause Macrocytic anemia if the dosage is exceeded.
Macrocytic anemia is also seen in liver disease, alcoholism, or in the case of hypothyroidism. In the laboratory, Macrocytic anemia is diagnosed with the Mean Corpuscular Volume (MCV) of the red blood cell reaches greater than 100.