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To determine the blood indices of clinical value.


1. Mean corpuscular volume (MCV), 2. Mean corpuscular haemoglobin (MCH),

3. Mean corpuscular hemoglobin concentration (MCHC), 4. Colour index


Blood indices help in the classification of different type of anaemias. They are calculated from the values of PCV, RBC count and haemoblobin content of blood.

Mean corpuscular volume (MCV): is the average volume of a single red cell expressed in cubic microns.

it is calculated as follows:


PCV in ml per litre of blood i.e_ PCV in ml xlO —


MCV = RBC count in million / cu. mm of blood RBC count in millions! cu. mm

Normal value is 86 ± 10 cubic microns (+1). An RBC with normal MCV is a normocyte, that with increased MCV is a macrocyte. eg:- in Pernicious anaemia and that with a decreased MCV is a microcyte. eg: Iron deficiency anaemia

Mean corpuscular haemoglobin (MCH): is the average amount of haemoglobin contained in a single red cell and expressed in micrograms (picograms). It is calculated as follows:

Hb in qm per litre of blood i.e Hb in qm xlO

MCH = RBC count in million / cu. mm of blood RBC count in millions! cu. mm


Normal value is 29 ± 2 micrograms (Picograms). RBC having normal MCH is normochromic, that with decreased MCH is hypochrom ic eg: Iron deficiency anaemia.

Mean corpuscular hemoglobin concentration (MCHC):

It is the haemoglobin concentration in red cell expressed an percentage or red cell volume. Hbinqm!dlofblood


Normal value is 34 ± 2 gm% MCHC is decreased in iron deficiency anaemia. Here MCV and MCH are decreased, but MCH is decreased out of proportion to the reduction in cell volume. So MCHC is decreased and the cell is not fully saturated with haemoglobin.


In pernicious anaemia, MCHC remains normal, since MCV and MCH increase proportionately. The cell is fully saturated with haemoglobin. Under no circumstances the value of MCHC can exceed the upper limit of normal, because the RBC cannot be supersaturated with haemoglobin.


Colour Index:


Colour index represents the amount of haemoglobin in each red cell as compared with the haemoglobin content of a normal red cell.


Calculation: For determing the colour index, the haemoglobin content of blood in gm/dl and the number of red cell in millions/cm m are first determined. The percentage of each is then calculated taking 14.5gm of haemoglobin/dl and 5 million of red cells/cmm as 100 percentage. The colour index is then calculated as follows:

Hb content expressed as a % of normal


Colour Index = RBC count expressed as a % of normal



1. Enumerate the test you will do in a case of Anaemia

2. Among the 3 blood indices, which is the most accurate? Why?