- Lab 17 -
Introduction
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Red blood cell indices are measurements that describe the size
and oxygen-carrying protein (hemoglobin) content of red blood
cells. The indices are used to help in the differential diagnosis
of anemia.
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The relationships between the hematocrit, the hemoglobin
level, and the RBC are converted to red blood cell indices
through mathematical formulas.
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The indices include these measurements:
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Mean corpuscular volume (MCV);
Mean corpuscular hemoglobin (MCH);
Mean corpuscular hemoglobin concentration (MCHC).
Purpose
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Anemia includes a variety of conditions with the same outcome:
a person's blood cannot carry as much oxygen as it should.
 A healthy person has an adequate number of correctly sized red blood
cells that contain enough hemoglobin to carry sufficient oxygen to all
the body's tissues.
 An anemic person has red blood cells that are either too small or too
few in number. As a result, the heart and lungs must work harder to
make up for the lack of oxygen delivered to the tissues by the blood.
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Anemia is caused by many different diseases or disorders. The
first step in finding the cause is to determine what type of
anemia the person has. Red blood cell indices help to classify
the anemia's.
Mean Corpuscular Volume
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These size categories are used to classify anemia.
 Normocytic anemia have normal-sized cells and a normal MCV.
 Microcytic anemia have small cells and a decreased MCV.
 Macrocytic anemia have large cells and an increased MCV.
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Microcytic cells are found in:
 Patients with iron deficiency anemia.
 Thalassemia.
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Macrocytic cells are found in:
 Patients with liver disease or hypothyroidism
 When there is asynchrony in RBC maturation (termed Megaloblastic
anemia's).
 Folate and vitamin B12 deficiencies.
Mean Corpuscular Hemoglobin
(MCH)
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Mean Corpuscular Hemoglobin
Concentration (MCHC)
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Values of normochromic cells range from 32 to 37g/dL.
Hypochromic cells are less than 32g/dL, and those of
hyperchromic cells are greater than 37g/dL.
 Hypochromic erythrocytes occur in thalassemia and iron
deficiency.
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Because there is a physical limit to the amount of hemoglobin
that can fit in a cell, there is no hyperchromic category, a cell
does not really contain more than 37g/dL of Hb, but its shape
may have become spherocytic, making the cell appear full.
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An MCHC > 37g/dL should be scrutinized carefully for an
error in Hb value.
Summary of red cell indices in
common anemia's
Type of Anemia
MCV
MCH
MCHC
Normocytic Normochromic
N
N
N
Microcytic Hypochromic
D
D
D
Macrocytic Normochromic
I
I
N
N= Normal
D= Decreased
I= Increased
Key Terms
Anemia
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A variety of conditions in which a person's blood can't carry as
much oxygen as it should due to a decreased number or size of red
blood cells.
Hypochromic
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A descriptive term applied to a red blood cell with a decreased
concentration of hemoglobin.
Macrocytic
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A descriptive term applied to a larger than normal red blood cell.
Mean corpuscular hemoglobin (MCH)
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A measurement of the average weight of hemoglobin in a red
blood cell.
Mean corpuscular hemoglobin
concentration (MCHC)
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The measurement of the average concentration of hemoglobin in a
red blood cell.
Mean corpuscular volume (MCV)
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A measure of the average volume of a red blood cell.
Microcytic
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A descriptive term applied to a smaller than normal red blood
cell.
Normochromic
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A descriptive term applied to a red blood cell with a normal
concentration of hemoglobin.
Normocytic
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A descriptive term applied to a red blood cell of normal size.
Red blood cell indices
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Measurements that describe the size and hemoglobin content
of red blood cells.