What is thalassemia ?
Thalassemia are a group of inherited blood disorders that are known to result in anemia. This disorder is associated with an individual’s capacity to produce hemoglobin, a protein in red blood cells that carries oxygen to the various parts of the body.
What is the prevalence of thalassemia?
According to the NIH, it is estimated that about 100,000 babies across the world are affected with severe thalassemia. Individuals with Southern Asian, Italian, Greek, Middle Eastern and African ancestry are known to be at a higher risk for this condition.
What are the different types of thalassemia?There are mainly 2 different types of thalassemia based on which oxygen carrying protein part of hemoglobin is affected-
- Alpha
- Beta
The inheritance pattern for both these types of thalassemia are the same. Children of affected parents inherit the genetic variant associated with the condition. The child will exhibit the condition only when both the copies of the risk variant are present. A child with a single affected variant will lead a healthy and normal life but could pass on the risk variant to the offspring.
The prevalence of carriers of thalassemia is about 1 in 14 individuals. The treatment provided for people detected with thalassemia is frequent blood transfusion and blood chelation therapy. This has helped in improving the quality of people affected with this condition. This has helped in transforming thalassemia from being a fatal condition to one that can be managed. The life expectancy for individuals detected with thalassemia is between 25 to 55 years, however, the increase in life expectancy is also associated with certain complications.
There are multiple genetic variants associated with thalassemia that have been characterized. This has helped in screening over 90% of individuals who have thalassemia, however, there are still 10% of mutations that haven’t yet been determined.
Genetic testing in thalassemia detection
The advent of micro-array technology and PCR methods have resulted in better detection and characterizations of thalassemia.
NIPD assay: Non invasive Prenatal diagnostic (NIPD) assay has been developed to detect β-thalassemia, which is based on the detection of genetic variants inherited form the father, using the arrayed primer extension (APEX) method .
SNP based mutation detection: This is one of the most commonly used genetic testing method for detecting beta thalassemia.
Gene therapy for thalassemia
Gene therapy for thalassemia faces several challenges as there are multiple genes associated with the production of hemoglobin. The expression of these genes are also restricted to a certain fraction of the bone marrow cells, which are essentially stem cells which could give rise to macrophages, or granulocytes or erythrocytes.
Prevalence of genetic variants associated with thalassemia in India
There are differing prevalence statistics among the different populations in India, due to the genetic diversity in India. The IVS-1-5 mutation is one of the most common mutation and is present in 22.8 to 81.4% in different populations in the homozygous state (2 risk variants). This mutation is found most commonly in Tamil Nadu among the South-East states of India. The 619p deletion is the most common mutation among the North-West states in India.
A study conducted by Verma IC (2000) showed that B thalassemia is one of the most common single gene disorder in india. Another study conducted by Bashyam MD et al (2004) found that nearly 10% of people with thalassemia were born in India every year.
There are more than 200 thalassemia mutations which have been detected but 28 of these mutations have been documented in India. About 90 to 94% of thalassemia patients in India report one of these mutations
- IVS1
- 619p deletion
- Frameshift mutation 8/9
- Codon 41/42
- A non-sense mutation in codon 15
Communities at higher risk for beta thalassemia
There are certain population in India with a higher risk of having beta thalassemia and they are the Bengalis, Sindhis and the Gujaratis. The incidence among these population was between 1 to 17%. The prevalence of this condition in India has been estimated to be 1.2 per 1000 births, which is 32,400 babies with a serious hemoglobin disorder in India.
There is a significant health burden caused by thalassemia which reinforces the need for early detection. There are 2 ways that detection could help people who carry these mutations:
- Early detection could help in providing better nutrition for high risk individuals and other treatment measures, so that fatality risk is reduced.
- Carrier detection could reduce the load of mutant alleles in the gene pool and for making an informed choice.
How much does the beta thalassemia test cost?
The risk for beta thalassemia is provided in Xcode’s health report. Beta thalassemia test cost (health report) INR 10,900.
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