Red Blood Cell Indices (MCV, MCH, MCHC) 8

RED BLOOD CELL INDECES
(MCV, MCH, MCHC)

Mean Corpuscular Volume (MCV)
The average volume of a red cell is found by dividing the volume of red cells in one litre of blood. This is termed the Mean Corpuscular Volume (MCV).






Normally, MCV = L = 90 * 10 -15 = 90 femtolitres (fl)


A higher than normal red cell volume indicates that the red cells are larger than normal, i.e. macrocytosis.
A lower than normal red cell volume indicates that the red cells are smaller than normal, i.e. microcytosis.



Mean Corpuscular Haemoglobin (MCH)
The average amount of haemoglobin in a red cell is determined by dividing the amount of haemoglobin in one litre of blood by the number of cells in one litre of blood. This is termed the Mean Corpuscular Haemoglobin (MCH).
Hb
MCH=___________________
No. of RBCs


Normally, MCH = = 30 * 10 -12 = 30 picogram (pg)


(Where one pigogram = one micromicrogram = 10 -12 g)




Mean Corpuscular Haemoglobin Concentration (MCHC)
The mean corpuscular haemoglobin suffers from the disadvantage that it does not take into account the cell size. Large cells tend to contain more haemoglobin that small cells. A better indication of the haemoglobin content of a red cell is found by dividing the haemoglobin content by the haematocrit. This gives the quantity of haemoglobin in a given volume of red cells, i.e. it is a concentration. It is termed the mean corpuscular haemoglobin concentration (MCHC).

Hb
MCHC= ______________
PCV


Normally, MCHC = g/l = 330 g/l = 33 g/dl


A low MCHC is found in a severe iron deficiency anaemia.


RELATIONSHIP BETWEEN INDICES:

It will be noted that when all are expressed as per litre:

MCH = MCHC * MCV


Since:
Hb Hb PCV
__________________ = _________ × _________________
No. of RBC PCV No. of RBC






Table *: Normal Values of Red Blood Cells Parameters

RBCs Parameters Mean ± S.D
RBCs count
Men
Women
Children 1.5 ± 1.1 (X 106 / mm3)
1.8 ± 1.0
4.7 ± 0.7
Hb
Men
Women
Children
15.5 ± 2.5 (g / 100 ml)
14.0 ± 2.5
13.0 ± 1.5
PCV
Men
Women
Children
0.47 ± 0.07 (%)
0.42 ± 0.05
0.41 ± 0.04
MCV
Adults
Children
85 ± 9 (fl)
84 ± 7
MCH
Adults
29.5 ± 2.5 (pg)
MCHC
Adults & Children
33.0 ± 2 (g/100 ml)
Mean diameter of red blood cell in dry blood film 6.7 – 7.7 ?m
Reticulocyte
Adults & Children 0.2-2.0 %