Carrier Detection of Thalassaemia and Haemoglobinopathies in Tribal Population of Bangladesh

Tribal population constitutes 1.8 percent of total population of Bangladesh. The study was conducted in the tribal population of Bangladesh to detect haemoglobinopathies and beta thalassemia trait. Another purpose of the study was to create awareness about thalassaemia and haemoglobinopathies among these indigenous groups. It was a cross sectional study conducted from September 2015 to November 2015. A total of 460 random samples were collected from three tribal groups, 175 cases from Chakma, 187 cases from Garo and 98 cases from Marma. Two cc of venous blood were collected in EDTA tube. Haemoglobin variants were studied by HPLC method using Variant Hemoglobin Testing System (Variant II Beta Thalassemia Short Program). Statistical analysis was carried out using SPSS statistical package (version 15). Data was analyzed by frequency distribution. Abnormal Haemoglobin variants were seen in 287 cases (62.4%) out of 460 cases and only173 cases (37.6%) showed normal haemoglobin pattern. Haemoglobin E trait was the most common abnormality seen in 164 cases (35.6%) followed by Haemoglobin E disease which was seen in 101 cases (22%), Beta thalassaemia trait was seen in 22 cases (4.8%). This study shows a high percentage of Haemoglobin E trait and Haemoglobin E disease. Beta thalassaemia trait is also higher in comparison with randomly selected general population of Bangladesh. After calculating the estimate burden of child born per year by Harding Weinberg equation, it was to be found that the significant result which shows that 1552 new haemoglobin E beta thalassaemia and 22 new beta thalassaemia patients born per year in the tribal population. So, the tribal population should be properly screened and counseled for thalassaemia and haemoglobinopathies.


Introduction
Thalassemia and haemoglobinopathies are the most common congenital disorders in the world. 1 Thalassemia have an autosomal recessive pattern of inheritance. Genetic diseases like thalassaemia are becoming an increasing health problem in developing countries as the deaths of children are falling due to better health services, vaccination against infectious diseases and improvement in nutrition. 2 Although reliable data are still lacking from many regions of the world, recent data indicate that about 7% of the world populations are carrier of haemoglobin disorder and about 300,000-500,000 children are born each year with the severe homozygous states of these diseases. 3 World Health Organation (WHO) data shows carrier status of Beta thalassaemia trait to be 3% and Hb E trait to be 4%. However, much of the data available from World Health Organization was based on studies that were carried many years ago and no regional data are available. 3 Another study done in school children of different divisions of Bangladesh showed beta trait frequency 4.1% and Hb E trait 6.1%. 2,4 This study also included frequency study of 44 tribal school children where 22% were found Haemoglobin E trait and 3% were found Beta trait. 2 The total population of indigenous ethnic minorities in Bangladesh was estimated to be approximately 1.58 million out of 152.52 million total population in 2011 (last census) which represents 1.8% of total population. 5 They comprise of diverse ethnic communities including Australoid, Tibeto-Burman and Sino-Tibetan races. Different ethnic groups of Bangladesh and their colorful lifestyles have significantly enriched the entire culture of Bangladesh. 6 They are closely knit people marrying within their clans and therefore highly vulnerable to many hereditary disorders causing high degree of morbidity and mortality. As the frequency of thalassemia is increased by the consanguinity and endogamous mating, it may be assumed that the tribal communities are facing the problem at a very large scale. It is therefore very important to know their status of thalassaemia and haemoglobinopathies.
In Bangladesh, there are about 45 different tribal groups spread across the country. 7 Chakmas are the largest ethnic group in Bangladesh. They live in Rangamati, Khagrachhari and Bandarban of Greater Chittagong Hilltracts, they also live in Teknaf of Coxsbazar. They are ancestor of mongoloid. 8 Marmas are the second largest ethnic group. Majority of them live in Rangamati, Khagrachhari and Bandarban, some of them also live in costal area of Teknaf and Patuakhali. 7 Marmas belong to the mongoloid races. 9 Garo population is another large indigenous communities in Bangladesh. 10 They live in the north-eastern part of Bangladesh, with the highest presence in the Gazipur, Mymensingh, Netrokona, Tangail, Sherpur, Jamalpur and Sylhet districts. 11 There is no accurate information about the ancestosr of Garos. But anthropologists presume that Garos belong to the Tibet-Burmese people of the Mongoloid race. 8

Materials and Methods
It was a cross sectional study. Study period was three months, from September 2015 to December 2015. Samples were collected from three major tribal groups Chakmas, Garos and Marmas. The samples were tested in Dhaka Shishu Hospital Thalassaemia and DNA Laboratory.
An educational session was given regarding thalassaemia and importance to know about carrier of thalassaemia and other haemoglobinopathies. The educational session also highlighted that marriage should be discouraged between carriers to prevent thalassaemia.
Sample collection and preparation: Two milliliters (2 ml) of venous blood was collected in a tube containing EDTA which were stored at 2-8 degrees Celsius and tested within three days. No preparation was required. HbA2/F calibrators and normal and abnormal controls were analyzed at the beginning of each run.   It was seen that haemoglobin E disease were most common among Garos.

Discussion
This study showed that there was high frequency of haemoglobin E trait and haemoglobin E disease in the tribal groups, beta thalassaemia trait was also little bit higher in comparison to the randomly selected general Bangladeshi population.

Conclusion
This study reveals that there was high frequency of Hb E trait and Hb E disease in the tribal population of Bangladesh and its coinheritance with beta thalassaemia trait will give birth to significant number of thalasaemic children in this population. The result in this study showed that a total of 1574 (Hb E beta thalasemia and beta thalassaemia major) children are born every year in this population. So, the tribal population should be properly screened and counseled for thalassaemia and haemoglobinopathies. They should be discouraged to marry between haemoglobin E trait and beta thalassaemia trait or between haemoglobinm E disease and beta thalassaemia trait. A large study needs to be done including all the tribal population in Bangladesh.