Genetic Testing for Beta Thalassemia – What You Need To Know

Thalassemia is 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. It is a highly heritable condition. A genetic test for beta-thalassemia not only helps with the diagnosis, but also predicts the risk of your children inserting the condition. 

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 at higher risk for this condition. 

What are the different types of thalassemia? 

There are mainly two different types of thalassemia based on which oxygen-carrying protein part of hemoglobin is affected:

  1. Alpha
  2. Beta

The inheritance pattern for both these types of thalassemia is 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. 

Genetic Testing For Beta Thalassemia

The treatment provided for people detected with thalassemia is frequent blood transfusion and blood chelation therapy. 

This treatment 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 has an association 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 microarray 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 from the father, using the arrayed primer extension (APEX) method.

SNP based mutation detection: A common genetic test for detecting beta-thalassemia.  

Gene therapy for thalassemia

Gene therapy for thalassemia faces several challenges, as there are multiple genes with an association to the production of hemoglobin. 

The expression of these genes is also restricted to a certain fraction of the bone marrow cells, which essentially stem cells that 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 mutations and is present in 22.8 to 81.4% in different populations in the homozygous state (2 risk variants). 

This mutation is common 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 disorders 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. 

More than 200 thalassemia mutations have been detected, but only 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

GenotypeRisk Implication
CCLow risk for thalassemia
CTModerate risk for thalassemia (possible carrier)
TTHigh risk for thalassemia

Communities at higher risk for beta-thalassemia

There is a 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 populations 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 that thalassemia causes, which reinforces the need for early detection. 

There are two 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, thereby reducing the fatality risk 
  • 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.

 

Updated 25 July, 2020

 

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