The McGill Physiology Virtual Lab

Blood Laboratory

Blood cell indices > MCV and MCHC
Excessively low values of red blood cell count, hematocrit, or hemoglobin may be indicative of anemia (i.e. decreased oxygen carrying capacity of blood). There are many different causes of anemia (e.g. loss of blood through hemorrhage, bone marrow disease, iron deficiency, vitamin B12 deficiency, or folic acid deficiency, etc.) and some of those are characterized by typically very small or very large red blood cells or reduced hemoglobin concentration in each cell.

Diagnosis of the type of anemia may be assisted by relating the measurements of red blood cell count, hematocrit and hemoglobin to derive the mean corpuscular volume (MCV) and the mean corpuscular hemoglobin concentration (MCHC).

Erythrocytes that have a normal size or volume (normal MCV) are called normocytic,

When the MCV is high, they are called macrocytic.

When the MCV is low, they are termed microcytic.

Erythrocytes containing the normal amount of hemoglobin (normal MCHC) are called normochromic.

When the MCHC is abnormally low they are called hypochromic, and when the MCHC is abnormally high, hyperchromic.

The terms above are used together to describe different forms of anemia. For example, iron deficiency anemia is described as microcytic and hypochromic, whereas vitamin B12 deficiency is macrocytic and normochromic.
Procedure
To calculate the MCV, expressed in femtoliters (fl, or 10-15L), the following formula is used:

To calculate the MCHC, expressed as grams of hemoglobin per 100 ml packed cells, the following formula is used:

The normal ranges for MCV and MCHC are as follows:
 MCV MCHC Female: 80-95 fl 30-34 gHb/100ml Male: 80-95 fl 30-34 gHb/100ml
Sample problem: calculate the MCV and the MCHC for a subject with a red blood cell count of 4x106 per cubic mm, a hematocrit of 40% and a hemoglobin concentration of 12 g/dl. Describe the subject's red cells: are they normocytic? normochromic?