What is alpha-thalassemia?
Alpha-thalassemia (α-thalassemia) is one of the most common inherited blood disorders. It reduces the production of functional hemoglobin, which is responsible for carrying oxygen throughout the body. As a result, affected individuals can have mild to severe anemia (shortage of red blood cells). The most severe type of α-thalassemia is known as hemoglobin Bart hydrops fetalis syndrome (Hb Bart syndrome). Most babies with Hb Bart syndrome are stillborn or die soon after birth.
What causes alpha-thalassemia?
Deletion mutations of the α-globin genes lead to reduced production of α-globin, a component of hemoglobin. Each person has two copies (alleles) of the two α-globin genes (HBA1 and HBA2). If only 1 of 4 alleles is deleted, the individual is a silent carrier and does not show any symptoms of α-thalassemia. People with 2 – 4 alleles deleted have mild to severe type of α-thalassemia.
How common is alpha-thalassemia?
It has been estimated that 3 – 5% of the Southern Chinese population are carriers of HBA1 and HBA2 deletion mutations. These mutations can be transmitted to the next generation. If both parents are carriers, they have a chance of giving birth to baby with severe form of α-thalassemia. Therefore, screening of α-thalassemia carrier or prenatal testing for pregnancies is highly recommended.
What is this test for?
This test detect the 3 most common deletion alleles of the α-globin genes (--SEA, -α3.7 and -α4.2) found in the Hong Kong population. These account for more than 96% of α-thalassemia-associated alleles in Hong Kong.
Who should consider this test?
Factor(s) known to affect results