OVERVIEW:
What is thalassemia?
It is an inherited blood disorder that is passed from parents to children. It is caused by mutations in DNA of cells which are making hemoglobin (protein present in red blood cell responsible for oxygen transport) i.e. it changes the amount & type of hemoglobin that body produces.
What is DNA mutation for thalassemia in blood lab test?
Thalassemia patients have 1 or more inherited genetic mutations which causes decrease production of normal hemoglobin. For hemoglobin, there are 4 genes in DNA which code for alpha globin chains & two genes (each) for beta, delta & gamma globin chains. The thalassemia patient has mutations in either alpha or beta globin genes. This laboratory test is therefore done to confirm the DNA mutations (change in DNA sequence) in alpha & beta globin-producing genes.
Why is DNA mutation for thalassemia in blood lab test done?
In thalassemia if there is DNA mutation in alpha globin-producing gene then it is called alpha-thalassemia. While in beta thalassemia there is mutation in beta globin-producing gene. The test is done:
- As it directly examines alpha &/or beta globin genes
- It is only way to determine silent alpha thalassemia trait & related Hb trait called hemoglobin constant spring.
- As an option for prenatal testing (to detect if baby is likely to have birth defects)
- Important to know thalassemia trait status in people of reproductive age or in family planning
- Which mutations lead to thalassemia?
It is inherited disease which results from mutations in ?- and ?-globin gene clusters on chromosome 16 and chromosome 11. There is absence or reduced synthesis of globin chains in Hb.
- Is fasting necessary before thalassemia test?
Yes, an overnight fast is preferred. Also avoid iron supplements for 24 hours before the sample collection
- At which age can thalassemia be diagnosed?
Children with moderate to severe thalassemia mostly receive diagnosis by age 2 years. While some people don’t have symptoms and they are carriers, i.e. when they have a child with thalassemia, they come to know.
- What does thalassemia do to RBCs?
Thalassemia is followed by destruction of large number of RBCs. It causes spleen enlargement & work harder than normal. Enlarged spleen can make anemia worse & reduces life of transfused RBCs.
INTERPRETATION OF THE RESULTS:
“Beta thalassemia”: For this HBB (hemoglobin beta) gene is analyzed or sequenced to confirm presence of thalassemia-causing mutations. There are about more than 250 mutations associated with beta-thalassemia with some not producing any symptoms. Presence of one of these mutations confirm diagnosis. These mutations indicate that there is wither decrease production of beta globulin or they prevent its production completely.
- “Alpha thalassemia”: Here two alpha genes HbA1 & HbA2 are detected. If there is mutation in two copies of each of these genes, then it means there if functional loss of one or more alpha genes & confirms alpha thalassemia.
This test is simply done to confirm DNA mutations in alpha globin-producing genes. It can be ordered before family planning, for healthy pregnancy, and for own health matters.