Mean Corpuscular Volume (MCV) Calculator

How does this mean corpuscular volume (MCV) calculator work?

This health tool calculates the average size of the red blood cells in a blood sample, the Mean Corpuscular Volume (MCV) which is one of the three RBC indices and considered the most important. The other two are Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC).

The MCV can be measured through automated hematology analysis or can be calculated in the MCV calculator as follows:

MCV in fL = (Hematocrit %)/(RBC x 10¹²/L) x 10

What is obtained through the formula above is the volume of blood by the proportion of cellular parts divided by the number of erythrocytes.

The measurement unit is the femtoliter (10^-15 L) and according to the American Association for Clinical Chemistry, normal values range between 80 and 96 fL, while other sources range between 80 and 100 fL or 83 and 97 fL.

Table with normal values for hematocrit, RBC and MCV:

Normal MCV values do not necessarily guarantee the absence of anemia. Normocytic anemia occurs when the size of the red blood cells is within norms but other RBC indices may be abnormal.

Causes of this type of anemia include:

■ Sudden blood loss (when the bone marrow hasn’t yet responded to the change in volume);

■ Hemolysis;

■ Presence of sepsis;

■ Malignancy;

■ Kidney failure;

■ Presence of prosthetic heart valves.

The MCV blood test takes place as standard in any complete blood count. This means that a needle is gently inserted in one of the veins usually of the arms, followed by the transfer of a small sample of blood through a tube in a recipient that will be then sent for testing.

While most subjects experience a sensation of prick, some may experience moderate pain or discomfort. There are no major health risks with this current but invasive procedure when all instructions are followed.

While the main purpose to calculate MCV is the differentiation of anemias, the parameter also allows the calculation of the Red Blood Cell Distribution Width (RDW).

Elevated MCV

This occurs when erythrocytes are larger than normal and may indicate macrocytic anemia (pernicious anemia). Here MCV values can go as high as 150 fL. This is a type of anemia most likely caused by:

■ B12 deficiency;

■ Folate deficiency;

■ Chemotherapy.

High MCV values have also been associated with an elevated GGT and AST:ALT of 2:1, signs of alcoholism.

A false elevation has been noted in the presence of RBC agglutination (in paraproteinemia) or in severe hyperglycemia (due to the abnormal swelling of the erythrocytes).

Low MCV

This indicates that the red blood cells are smaller than normal and is consistent with microcytic anemia, a condition likely to be caused by:

■ Iron deficiency (inadequate diet intake);

■ Gastrointestinal blood loss;

■ Thalassemia;

■ Chronic diseases.

In this case, MCV can go as low as 60 fL.

Example of a calculation

Question: Given a hematocrit value of 43% and a red blood cells count of 4.1 x10¹²/L what is the MCV?

Answer: MCV in fL = 43/4.1 x 10 = 104.87 fL (rounded to 104.9 fL).

References

1) The McGill Physiology Virtual Lab (2016) Blood cell indices > MCV and MCHC.

2) Williams WJ. Examination of the blood. In: Williams WJ, Beutler E, Erslev AJ, Lichtman MA, eds. Hematology, 3d ed. New York: McGraw-Hill, 1983;9–14.

3) Bessman JD, Gilmer PR Jr, Gardner FH. (1983) Improved classification of anemias by MCV and RDW. Am J Clin Pathol; 80(3):322-6.

4) Vajpayee N, Graham SS, Bem S. Basic Examination of Blood and Bone Marrow. McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd. Elsevier/Saunders: Philadelphia, PA; 2011. 30.

5) Briggs C, Bain BJ. Basic Haematological Techniques. Bain BJ, Bates I, Laffan M, Lewis SM. Dacie and Lewis Practical Haematology. 11th ed. Philadelphia, PA: Churchill Livingstone/Elsevier; 2012. chap 3.

6) Tønnesen H, Hejberg L, Frobenius S, Andersen JR. (1986) Erythrocyte mean cell volume--correlation to drinking pattern in heavy alcoholics. Acta Med Scand; 219(5):515-8.