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Showing posts with label hemo. Show all posts
Showing posts with label hemo. Show all posts

Hemoglobin A2 the clinical significance

Haemoglobin is the substance in the blood that carries oxygen around the body. The type of Adult haemoglobin in person is determined by the inherited genes from parents. Genes always come in pairs one from the father and one from the mother. Hence, every individual inherits two Adult Haemoglobin genes. The normal and most common Adult haemoglobin gene combination that an individual can inherit from their parents is Haemoglobin AA and is written as Hb AA.
Hemoglobin A2 (HbA2) is a normal variant of hemoglobin A .It has two alpha and two delta chains (α2δ2) and is found at low levels in normal human blood.The biological role of this protein is not yet known.
During the early embryonic period itself this is produced in the fetus, irrespective of the type of major Adult haemoglobin they have inherited from their parents.
From very early life in the womb the level of Haemoglobin A2 is between 1.5% – 3.5% and remains at this level at birth and through out adulthood.So in adult also the  normal amount of Hemoglobin A2 is 1.5-3.1% of all hemoglobin molecules, Hemoglobin A2 level vary depending on the underlying disease
Clinical significance of Hemoglobin A2
Haemoglobin A2 is a redundant haemoglobin because  this is  not an efficient at carrier of  oxygen in  the body, however, But it has certain clinical significance because it is useful for helping the laboratory to diagnose some genetic mutations of haemoglobin, based on the type of genetic mutation  and underlying disease the level of A2 will rise or fall.
Causes of Increased HbA2 levels
  • Beta thalassemia
  • Sickle cell anemia
  • Megaloblastic anemia
  • Hyperthyroidism
  • Unstable Hemoglobinopathies
  • Malaria (doubtfull cases) 
Causes of Decreased HbA2 levels
  • Iron deficiency Anemia
  • Alpha thalassemia
  • Delta thalassemia
  • Sideroblastic anemia
  • Myelodysplastic syndromes
  • Acute myelocytic leukemia (minor reduction)
  • Hb Lepore