Table of Contents

Calculation of blood indices (RBC indices)
1. Mean Corpuscular Volume (MCV)

It is the average volume of a single red blood cell.

MCV = PCV[100 ml Of blood (Hct%)]/No. of RBC (in million) X 10

Normal: 78-94 cu

MCV Variation

Increased (>94) in

1. Megaloblastic anaemia

2. Spherocytosis

Decreased (<78) in

Iron deficiency anaemia

Clinical Significance

MCV is useful in laboratory classification of anaemia.

i) Microcytic anaemia (MCV <78 cu µ)

ii) Normocytic anaemia (MCV = 78-94 cu µ)

iii) Macrocytic anaemia (MCV >94 cu µ)

2. Mean Corpuscular Haemoglobin (MCH)

It is an average quantity or mean weight of Hb in a single RBC. In SI units, it is expressed as picogram.

MCH = Hb gm[100 ml]/ No. of RBC (in million) [cumm] X 10

Normal : 27-32 (picogram)/ug. MCH decreases in iron deficiency anaemia.

MCH decreases in iron deficiency anaemia.

Clinical Significance

MCH is useful in laboratory classification of anaemia. i) Normochromic anaemia (MCH =-: 27-32 pg) ii) Hypochromic anaemia (MCH <27 pg)

i) Normochromic anaemia (MCH = 27-32 pg) ii) Hypochromic anaemia (MCH <27 pg)

ii) Hypochromic anaemia (MCH <27 pg)
Concentration (MCHC)

3. Mean Corpuscular Haemoglobin Concentration (MCHC)

It is an average concentration of Hb in erythrocytes. It is a percentage of Hb in relation to packed cell volume.
MCHC = Hb gm[100 ml] / PCV[lOO ml] X 100

Normal: 32-38%.

Clinical Significance

Normochromic anaemia (MCHC = 32-38%)
Hypochromic anaemia (MCHC <32%)

If MCHC is less than 32, then we call it as hypochromic RBC, and it is present in iron deficiency anaemia and thalassaemia.

4. Colour Index

It is the ratio of Hb% with RBC%.

Cl = Hb%/RBC count %

Normal: 0.85-1.15
The colour index is high in pernicious anaemia and low in iron deficiency anaemia.
It is clinically insignificant index because of wide variation in 100% Hb and 100% RBC count.