Mean Corpuscular Volume (MCV)

What sample is needed for Mean Corpuscular Volume (MCV)?

1. The best sample is EDTA blood.
2. Stable for 6 hours at 25 °C  and 24 hours at 4 °C.
3. Fetal blood is collected percutaneously from the umbilical area.

What are the indications for Mean Corpuscular Volume (MCV)?

1. This is one of the blood indices.
2. This is done to classify and diagnose anemia.
3. It is a useful screening test for occult alcoholism.

How would you define Mean Corpuscular Volume (MCV)?

• It represents an average measurement of RBC volume varying from 82 to 98 fL.
• Mean Corpuscular Volume (MCV) is manually calculated as hematocrit divided by RBC count.
• It can be measured directly by the automated instrument.

What are the facts about Mean Corpuscular Volume (MCV)?

1. MCV measures the effect of average RBC size on hematocrit.
2. Mean Corpuscular Volume (MCV) measures a single RBC’s average volume or size.
3. If the average size of RBCs increases, the same number of RBCs will have a slightly larger cell mass and a slightly increased hematocrit value. The opposite happens if the average size of RBCs is smaller than normal.
4. MCV indicates the volume occupied by a single RBC and is measured in a cubic micrometer of the mean volume.
   1. Cubic micrometer = femtoliter ( fL ).
5. MCV helps to classify various anemias.
6. Macrocytic RBC:
   1. When the RBC size is larger than normal, more than 100 fL.
7. Microcytic RBC:
   • When the RBC size is smaller than normal, it is less than 82 fL.
8. It is considered that the most common cause of macrocytosis is alcoholism with or without cirrhosis.

What is the normal Mean Corpuscular Volume (MCV)?

Source 1

Source 2

• Adult = 80 to 95 fL.
• Newborn = 96 to 108 fL

Another source

• Both sexes = 80 to 100 fL
• Heavy smoking  increases the MCV as much as 3 fL

What are the causes of increased Mean Corpuscular Volume (MCV)?

Macrocytic anemia causes are:

1. B12 or folic acid deficiency :
   1. Decreased ingestion.
      1. Laking animal protein.
      2. Vegetarians.
   2. Impaired absorption.
      1. Intrinsic factor deficiency.
      2. Abnormal intrinsic factor molecule.
      3. Patient with partial or total gastrectomy.
      4. Ileal resection.
      5. Sprue.
      6. Celiac disease.
      7. Intestinal lymphoma.
      8. Drug-induced malabsorption.
2. Parasitic infestation.
   1. Diphyllobothrium latum.
   2. Infected diverticula.
   3. Blind loop.
3. Increased requirement.
   1. Pregnancy.
   2. Malignancies.
   3. Hyperthyroidism.
   4. Chronic pancreatic disease.

Mean corpuscular volume (MCV): Macrocytic RBCs and hypersegmented polys.

What are the causes of decreased Mean Corpuscular Volume (MCV)?

Microcytic anemias are seen in:

1. Iron metabolism-related.
   1. Iron deficiency anemia.
   2. Decreased dietary intake.
   3. Malabsorption.
   4. Increased iron loss.
   5. Increased body requirements for iron.
   6. Congenital hypochromic microcytic anemia.
   7. Anemias of chronic diseases.
2. A defect in heme synthesis.
   1. Idiopathic refractory sideroblastic anemia.
   2. Acquired sideroblastic anemia.
   3. Hereditary sideroblastic anemia.
   4. Autosomal anemia ( X chromosome-linked ).
3. Disorder of globin synthesis.
   1. Thalassemia.
   2. Hemoglobinopathies.

What are the causes when the Mean Corpuscular Volume (MCV) is increased?

Macrocytic anemias are seen in:

1. Pernicious anemia (vit.B12 deficiency).
2. Folic acid deficiency.
3. Liver diseases.
4. Alcoholism.
5. Antimetabolic therapy.