RELATIONSHIPS BETWEEN RBC INDICES
RBC count
Used to calculate the Hct (Hct = MCV x RBC count)
b. Used by some to predict iron deficiency vs. thalassemia (e.g., Meltzer index)
b. Largely ignored because it says nothing about the size/Hbization of RBCs.
MCV
MCV is super helpful because it is the first branch point in the ddx of anemia - microcytic vs. normocytic vs. macrocytic. Each has its own specific causes.
Hct
The Hct is helpful to a point. As mentioned above it is calculated from the MCV and RBC count. Note that it is impervious to the content of the RBCs.
The only time the Hct is useful is in patients with polycythemia where the negative effects of Hct on blood viscosity (and therefore total peripheral resistance and cardiac output).
MCHC
Think about the MCHC as the degree of central pallor of the RBC - the more central pallor, the lower the MCHC. It is so much more useful than the MCH (which simply tracks with MCV and MCHC), the MCHC is the second branch point in the ddx of anemia.
RBC count
Used to calculate the Hct (Hct = MCV x RBC count)
b. Used by some to predict iron deficiency vs. thalassemia (e.g., Meltzer index)
b. Largely ignored because it says nothing about the size/Hbization of RBCs.
MCV
MCV is super helpful because it is the first branch point in the ddx of anemia - microcytic vs. normocytic vs. macrocytic. Each has its own specific causes.
Hct
The Hct is helpful to a point. As mentioned above it is calculated from the MCV and RBC count. Note that it is impervious to the content of the RBCs.
The only time the Hct is useful is in patients with polycythemia where the negative effects of Hct on blood viscosity (and therefore total peripheral resistance and cardiac output).
MCHC
Think about the MCHC as the degree of central pallor of the RBC - the more central pallor, the lower the MCHC. It is so much more useful than the MCH (which simply tracks with MCV and MCHC), the MCHC is the second branch point in the ddx of anemia.
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