Thalassemia is typically caused by sequence variants in the HBA1, HBA2 or HBB genes. Common sequence variants include Single Nucleotide Variants (SNVs), smaller insertion and deletions (indels) as well as large, exon spanning Copy Number Variations (CNVs). A range of different techniques such as GAP-PCR, Sanger sequencing, reverse hybridization and MLPA is traditionally required to assess all variants.
Relying on a patchwork of methods presents a range of challenges such as:
- Long turn-around times to get an overview of both alpha and beta thalassemia sequence variants in a patient
- Resource-intensive and costly processes to validate, maintain and train operators on all assay types
- Risk that sequence variants remain undetected if the workflow is terminated when a first sequence variant is found, or a method is used where only sequence variant-specific detection is possible
- Risk for sample contamination and mix-up when handling multiple tubes and protocols.
Detect all sequence variants with a single assay
If a genetic testing workflow is terminated when a first sequence variant is found, or a method is used where only sequence variant-specific detection is possible, there is a risk that additional sequence variants remain undetected. A study shows that the Devyser Thalassemia NGS assay detects sequence variants that were not discovered with traditional thalassemia testing. Devyser’s kit was used to analyze 25 samples previously characterized to carry pathogenic sequence variants in the globin genes using traditional genetic testing methods and workflows.
- All previously detected pathogenic SNVs, indels and CNVs in the globin genes were confirmed using Devyser Thalassemia
- In 15% of samples, additional pathogenic sequence variants were found. The majority of these were found in a different globin gene. These sequence variants had previously not been identified since the workflow had been terminated as soon as a pathogenic sequence variant was found in the first gene cluster investigated
Thalassemias are hemoglobinopathies characterized by an abnormal hemoglobin production that can lead to anaemia and destruction of red blood cells. Alpha and beta thalassemia, the two main types of thalassemias are caused by inadequate production of the α- and/or ß-globin molecule.
Symptoms of thalassemia vary from mild, to severe andeven fatal. In 1990 more than 36,000 deaths were reported due to thalassemia. This had decreased to 16,800 in 2015 primarily due to national screening programs and family planning. Approximately 5% of the global population has a variant in the genes coding for the alpha or beta hemoglobin molecules. Of these, 34% have symptoms.
Alpha thalassemia is most common in sub-tropical and tropical areas. In certain ethnic groups, the prevalence can be as high as 30%, with up to 90% as carriers. Beta thalassemia is particularly prevalent among the Mediterranean, African and South Asian population. It is hypothesized that alpha and beta thalassemia are more prevalent in malaria exposed regions due to improved disease protection.