Red Blood Cell (RBC) Indices Calculator

How does this red blood cell (RBC) indices calculator work?

This health tool determines each of the three RBC indices based on patient hemoglobin, hematocrit and red blood cell count.

RBC indices are reported in the results of an automated blood count or can be calculated through formulas, which will be discussed below. They reflect characteristics of the circulating red blood cell population, thus offering information on size, shape and composition of the erythrocytes.

The main purpose in the determination of the RBC indices is the differentiation of anemias, the condition in which the number of RBCs or hemoglobin quantity within them fall below normal.

The RBC blood test involves a small venous blood sample taken through a needle connected to a tube, just like all blood tests. While most people experience a prick or stinging, for others, the discomfort may be of moderate pain. In some cases, a slight bruise may appear locally.

The three fields contained in the RBC indices calculator are:

■ Hemoglobin – measured in g/dL and representing the protein responsible for oxygen transport in the blood. Normal values are between 12 and 18 g/dL, with a slight variation for gender.

■ Hematocrit – expressed in percentage and representing the ratio of red blood cells to the total volume of blood. It is physically obtained as result of the centrifugation of the blood sample. Normal values range between 37 and 52%.

■ RBC – the number of red blood cells in the sample. This is a determination carried as part of the complete blood count CBC. It is measured in x10¹² cells/L or x10⁶ cells /mm³ and the normal range is between 4.2 and 6.3 x10¹²/L.

Quick table of RBC indices

Mean Corpuscular Volume (MCV)

This parameter offers information on the average size of the RBCs and is measured in femtoliter (which is 10^-15 L). 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.

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

The MCV is considered to be the most important of the RBC indices and allows the calculation of the red blood cell distribution width.

Normal MCV erythrocytes are called normocytic, high MCV are called macrocytic and low MCV microcytic:

■ Elevated MCV – larger than normal erythrocytes indicate macrocytic anemia with likely causes being B12 deficiency, folate deficiency or chemotherapy.

■ Low MCV – smaller than normal erythrocytes indicate microcytic anemia, likely to be caused by iron deficiencies, thalassemia or chronic diseases.

■ Normal MCV does not guarantee the absence of anemia as in the case of normocytic anemia, MCV values are normal while the other RBC indices may be abnormal. Normocytic anemia is likely to be caused by sudden blood loss, the presence of sepsis, malignancy, kidney failure or presence of prosthetic heart valves.

Mean Corpuscular Hemoglobin (MCH)

This parameter indicates the average weight of hemoglobin in the tested RBC population. The measurement unit for MCH is picogram (which is 10^-12 grams). According to the American Association for Clinical Chemistry, the reference range for adults is between 27 and 33 pg while other sources provide a range between 27 and 31 pg.

MCH in pg = (Hemoglobin in g/dL)/(RBC x 10¹²/L) x 10

Mean Corpuscular Hemoglobin Concentration (MCHC)

This parameter offers information on the average concentration of hemoglobin in the red blood cell sample. The reporting unit for MCHC is g/dL and according to the American Association for Clinical Chemistry, normal adult values range between 33.4 and 35.5 g/dL. Other sources present a wider range of 32 to 36 g/dL.

MCHC in g/dL = (Hemoglobin in g/dL)/(Hematocrit %) x 100

Abnormally low MCHC values indicate hypochromic RBCs, normal values are characteristic for normochromic cells and abnormally elevated MCHC values indicate hyperchromic erythrocytes.

Example of a calculation

Taking the case of a patient with the following RBC parameters:

■ Hematocrit = 43%;

■ Hemoglobin = 13.5 g/dL;

■ RBC = 4.6 x10¹²/L.

Results:

■ MCV in fL = 43/4.6 x 10 = 93.47 fL (rounded to 93.5 fL);
■ MCH in pg = 13.5/4.6 x 10 = 29.34 pg (rounded to 29.3 pg);
■ MCHC in g/dL = 13.5/43 x 100 = 31.39 g/dL (rounded to 31.4g/dL).

References

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

2) Sharma R. (1990) Chapter 152, Red Cell Indices. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.

3) 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.

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