Epidemiology of thalassemia among the hill tribe population in Thailand

Background Thalassemia is a severe disease that occurs due to abnormalities in hemoglobin genes. Various genetic factors in different populations lead to different clinical manifestations of thalassemia disease, particularly among people who have a long history of migration and who have married among tribes, such as the hill tribe people in Thailand. This genetic epidemiological study aimed to estimate the prevalence of various forms of thalassemia among the six main hill tribe populations in Thailand. Methods A cross-sectional study was conducted to obtain information and blood specimens from school children belonging to one of the six main hill tribes in Thailand: Akha, Lau, Hmong, Yao, Karen, and Lisu. Hill tribe children who were attending grades 4-6 in 13 selected schools in Chiang Rai Province, Thailand, were invited to participate in the study. A validated questionnaire and 3 mL blood specimens were collected after obtaining information consent forms from both the children and their parents on a voluntary basis. A complete blood count (CBC) was performed, followed by osmotic fragility (OF) and dichlorophenol indophenol precipitation (DCIP) tests to screen for thalassemia. High-performance liquid chromatography (HPLC) and real-time quantitative polymerase chain reaction (qPCR) were used to identify hemoglobin type and alpha-thalassemia, respectively. A t-test, chi-square and logistic regression were used to detect the associations between variables at the significance level of alpha = 0.05. Results A total of 1,200 participants from 6 different tribes were recruited for the study; 50.0% were males, and 67.3% were aged 11-12 years. The overall prevalence of thalassemia carriers according to the screening tests was 9.8% (117 of 1,200). Among the cases, 83 were A2A (59 cases were alpha-thalassemia 1 carrier or alpha-thalassemia 2 carrier or homozygous alpha-thalassemia 2, and 24 cases were beta-thalassemia trait with or without alpha-thalassemia); 1 case was EE (homozygous Hb E with or without alpha-thalassemia); 31 cases were EA (30 cases were the Hb E trait, and 1 case was Hb E trait with or without alpha-thalassemia); 1 case was A2A Bart's H (Hb H disease alpha-thalassemia 1/alpha-thalassemia 2); and 1 case was A2A with abnormal Hb. The prevalence of the alpha-thalassemia 1 trait among the hill tribe population was 2.5%. The greatest prevalence of the alpha-thalassemia 1 trait was found in the Karen (3.0%) and Hmong (3.0%) tribes. Conclusions The prevalence of some forms of thalassemia in the hill tribe population is higher than that in the Thai and other populations. Effective and available thalassemia screening tests, including essential information to protect the next generation through the specific counseling clinic, are crucial, particularly due to increasing marriages within these populations.

Automated summary

Thalassemia is a severe disease caused by abnormalities in hemoglobin genes, with higher prevalence in certain hill tribe populations in Thailand compared to the general population. Effective and available screening tests for thalassemia are crucial to protect the next generation, especially due to increasing marriages within these populations.