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1.2.5 Anatomy, Physiology, and Health Education I Laboratory

hemoglobin.jpg

Lab 4. Estimation of Haemoglobin with the help of Sahli's Haemoglobinometer

Developed by Prova Biswas

Theory

Haemoglobin is iron containing red pigments of the blood. It is the tetrapyrrole porphyrin ring, consisting of four heme moiety and four globin chain (96%). Heme is iron (present in ferrous $Fe^{++}$ state) containing pigments. Globin is a histone type protein. Haemoglobin carries the O2 from lung to tissue and the CO2 from tissue to lungs.

After the normal life span is over, the red blood cells are destroyed by the macrophages in liver, spleen or red bone marrow into heme moiety (biliverdin and iron) and globin protein. The iron and globin are recycled to reuse and the biliverdin is converted into the bilirubin which is further converted into the stercobilin to be removed in the feces. The colour of feces is yellow because of the presence of the stercobilin.

Types of Haemoglobin (Hb):

i. Adult Haemoglobin:
a. Hb A: It consists of two $\alpha$ chain and two $\beta$ chains in globin protein, $\alpha_2\beta_2$. 97% of adult Hb is of this type.
b. Hb A2 ($\alpha_2\delta_2$): Minor Hb A2 present in adult, the concentration of Hb increases in some types of anaemia.
ii. Fetal haemoglobin:

a. Hb F ($\alpha_2\gamma_2$): Hb F accounts for 70-90% of haemoglobin at term, 25% in one month, and 5% in six months. Hb F concentration in adults increases in some types of anemia, haemoglobinopathies, and some time in leukemia.
b. Haemoglobin Bart's($\gamma_4$): It's concentration increases in fetal life in thalassemia.
iii. Embryonic haemoglobin:
Hb Gower 1 ($\eta_2\epsilon_2$), Hb Gower 2 ($\alpha_2\epsilon_2$), and Hb Portland ($\alpha_2\gamma_2$).
iv. Abnormal haemoglobin:
a. There are four clinically important abnormal haemoglobins: Hb S, Hb C, Hb D, and Hb E, present in different hereditary haemoglobinopathies. The most commonly encountered hemoglobin is Hb S ($\alpha_2\beta_2$) where in the beta chain valine is substituted by glutamic acid at the sixth position. Hb S is present in sickle cell anemia.
b. Unstable haemoglobin are haemoglobin variants that undergo denaturation and precipitate in the red cells at Heinz bodies. These are present in a type of congenital nonspherocytic hemolytic anemia.

Clinical significance of haemoglobin count

Each RBC contains about 280 million of Hb, which is responsible for the transportation of oxygen and carbon dioxide (23%). The percentage of RBC in the blood is called the haemacrit which is clinically important. The normal range of haemacrit for male is 40-54% and it is 38-46% in case of female.

Normal range of Haemoglobin:

Male: 14-17 gms/dl of blood, Female: 12-14 gms/ dl of blood

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