MCV 80 - 95
MEAN CORPUSCULAR VOLUME (MCV)
This value represents a measurement of the size of the red blood cells. The normal values range from 80-94 fL in males and from 81-99 fL in females. The MCV is especially helpful in determining the etiology of an anemia with an inappropriately low reticulocyte index. Anemias with a low reticulocyte index are classified as macrocytic, normocytic, or microcytic when the MCV is elevated, normal, or depressed, respectively. This is helpful because it helps to narrow the differential diagnosis and direct which tests should be ordered next to help determine the cause of the anemia. A false elevation of the MCV may be seen in the presence of cold agglutinins, reticulocytosis, leukocytosis, hyperglycemia, and hypernatremia. Physiologic increases in the MCV occur with pregnancy, the use of oral contraceptives and after menopause. An elevated MCV may also be seen in persons who have ingested methanol.
Two calculations may be performed using the MCV to differentiate iron deficiency anemia from thalassemia. The first calculation is:
If the calculation yields a negative value, this is consistent with thalassemia. Conversely, a positive value is indicative of iron deficiency anemia. The second calculation is:
If the ratio is greater than 13, iron deficiency anemia is highly suspect whereas a ratio less than 13 is most consistent with thalassemia. The diagnosis should be confirmed with the appropriate tests.
When microcytosis is associated with a normal hemoglobin and hematocrit, the possibility of polycythemia vera should be entertained in patients of the appropriate age group. However, the same abnormality may be seen in patients afflicted with thalassemia minor. As above, the appropriate tests should be investigated to confirm the diagnosis.