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International Thalassaemia Day 2022: What Tests Are Done For Diagnosis Of This Blood Disorder?

International Thalassaemia Day 2022: What Tests Are Done For Diagnosis Of This Blood Disorder?

Be part of the International Thalassaemia Day 2022 and help transform the lives of millions of people suffering from this disease.

Written by Editorial Team |Updated : May 7, 2022 4:20 PM IST

The theme for the International Thalassaemia Day (ITD) 2022 is "Be Aware. Share. Care: Working with the global community as one to improve thalassaemia knowledge.'' The theme seeks to inspire every individual to contribute, at the personal level, to the fight against thalassaemia and share essential information and knowledge to support the best possible health, social and other care of patients with this disease.

Thalassemia is an inherited blood disorder which leads to reduction or absence of hemoglobin, a protein in red blood cells which carries oxygen. Along with hemoglobinopathies, where in the hemoglobin structure is affected, thalassemia is one of the most common inheritable single gene disorders in the world. According to the World Health Organization, around 5 per cent of the world populations are carriers of a potentially pathological hemoglobin (Hb) gene. In India, the prevalence of thalassemia trait is around 3-4 per cent, which is observed higher in the North-East, but because of consanguinity, caste, and area endogamy, some communities show a very high incidence, making this disease a public health problem of concern.

A retrospective analysis of samples from 106277 suspected patients, received between 2017 to 2019 at Metropolis Healthcare Ltd, yielded 18,936 (17.82 per cent) cases with abnormal hemoglobin variants. A high prevalence of Beta thalassemia trait is found among 9817 cases (9.23 per cent), which was followed by sickle cell trait disease in 2680 cases (2.52 per cent).

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There are two common types of thalassemia and , signs and symptoms depend on the type of mutation inherited. -thalassemia is a genetic disorder which is caused by mutations in the HBB gene on chromosome 11, patients with -thalassemia major have a severe or complete loss of -globin and become severely anaemic as the child hemoglobin level decreases during the first several months of life; repeated transfusions are necessary to sustain life. Patients typically present in early childhood with severe anaemia, hepatosplenomegaly, and failure to thrive. Individuals with thalassemia intermedia present later in life and have milder anaemia that requires transfusions only intermittently. Carriers of -thalassemia, on the other hand, have a single gene having 0/ + mutation with the other gene being normal and suffer from mild anaemia with normal life expectancy.

Alpha-thalassemia is caused by decreased synthesis of alpha-globin chains. Four alpha-globin genes are normally present (2 on each chromosome 16). Disease severity ranges from being a silent carrier to death of foetus depending upon number of mutations present.

Tests for diagnosis of Thalassemia

Role of laboratory in diagnosis of thalassemia is crucial when a suspecting physician sends a sample for peripheral smear in a patient suffering from mild to moderate anaemia seen in thalassemia carriers. A good laboratory should be able to pick up subtle clues offered by red blood cell (RBC) morphology, counts and should be able to recommend further tests i.e., iron and haemoglobin studies. In contrast, a thalassemia major patient is easy to pick both clinically and through laboratory findings. For detection and identification of type of hemoglobin disorder, a cation exchange high-performance liquid chromatography (CE-HPLC) should be offered to patients for best results.

However, for definitive diagnosis a study of mutations of beta globin gene and alpha thalassemia genes through molecular techniques is required. Polymerase chain reaction (PCR) with Sanger sequencing & Gap PCR are commonly used to detect such mutations.

Future in this segment lies with Next Generation Sequencing (NGS) which has capability to detect all mutations in a shorter time span. Though the prohibitive cost of the molecular tests has led to their underutilization, still they do find a special niche in wellness segment wherein a couple from thalassaemic family-history can plan pregnancy basis the genetic make-up of the foetus before actual implantation or during pregnancy.

The article is contributed by Dr. Vishal Wadhwa, Head of Scientific Affairs, Metropolis Healthcare Ltd.