Determination of hemoglobin in the blood

Determination of hemoglobin in the blood is one of the most basic laboratory tests. Blood hemoglobin is the main criterion for assessing whether anemia is present . The term anemia is used when hemoglobin or erythrocytes fall below the lower limit of physiological levels. Anemia is a very common clinical finding. This is a condition that leads to a reduction in oxygen binding capacity and a consequent tissue respiratory disorder.

Causes of anemia

Anemia occurs when erythropoiesis is unable to meet the requirements for new red blood cells. It develops as a result of blood loss or increased loss of red blood cells or insufficient red blood cell production. The following is a list of some specific causes of anemia:

1. Anemia from increased blood loss :
   • Acute blood loss.
   • Chronic blood loss.
2. Anemia due to increased erythrocyte breakdown (hemolytic conditions).
   • Autoimmune hemolytic anemia (presence of antibodies against own erythrocytes).
   • Erythrocyte membrane disorder (deviation in erythrocyte membrane composition).
   • Hereditary erythrocyte enzyme defects (pyruvate kinase, glucose-6-phosphate dehydrogenase).
   • Unstable hemoglobin - hemoglobinopathies (eg hemoglobin S in sickle cell disease).
3. Anemia from decreased erythrocyte production .
   • Lack of substances needed for erythropoiesis (iron deficiency, vitamin B12 deficiency, folic acid deficiency, erythropoietin deficiency - chronic renal diseases, lack of other substances such as vitamins B1, B6).
   • Anemia due to chemical, physical and radiation damage.
   • Anemia in chronic inflammatory, infectious and cancerous diseases.

Elevated hemoglobin levels may be a sign of dehydration or chronic decreased pulmonary ventilation. Rarely, it can be caused by some myeloproliferative conditions, such as polycythemia vera .

Principle of blood hemoglobin determination

Oxidation of hemoglobin to methemoglobin:

HbFeII	+	[FeIII(CN)6]3−	→	HbFeIII	+	[FeII(CN)6]4−
Hemoglobin				Methemoglobin

Conversion of methemoglobin to cyanomethemoglobin:

HbFeIII	+	CN−	→	HbFeIIICN
Methemoglobin				Kyanmethemoglobin

The photometric determination is based on the oxidation of ferrous iron in hemoglobin with potassium ferrocyanide to ferric iron. The resulting methemoglobin is converted to a very stable cyanomethemoglobin in a further reaction with potassium cyanide with a single broad absorption maximum in the visible region at 540 nm.

Assessment: The reference range for hemoglobin in the blood (B hemoglobin) for an adult male is 130-180 g / l and for a female 120-160 g / l.