A haemoglobinopathy is a condition (disease or trait) caused by a defect in the genetic code for hemoglobin synthesis, there are over 600 known hemoglobin variants reported. These variants are characterized as either qualitative or quantitative Haemoglobinopathies. This disorder is characterized by either reduced synthesis of one or more globin chain or synthesis of structurally abnormal variant hemoglobin.
The World Health Organization (WHO) estimates that globally at least 5% of adults are carriers for a haemoglobin condition: approximately 2.9% for thalassaemia and 2.3% for sickle cell disease. It means 5% of the world population is carriers of different inherited disorders of hemoglobin, making them the most common monogenic disease.
Classifications of Hemoglobinopathies
Qualitative defects are defined as structural variations that result in a change of the type of hemoglobin produced. 95% of the structural variants are caused by a single amino acid replacement. The amino acid replacement or substitution changes the quality, and specification of the hemoglobin. Each substitution changes the function of the hemoglobin molecule in a particular way.
Quantitative defects are characterized by a reduction or absence in the amount of normal alpha and/or beta globin chains produced. An example of a quantitative defect is beta thalassemia. When an individual has beta thalassemia trait, beta chains are being produced, but in a lesser quantity. Because individuals with quantitative defects may still have hemoglobin A, hemoglobin so we need combination of tools to diagnose such disorders.