Studi DNA Thalassemia-αº Southeast Asian Type di Medan

Abstract

It is well documented that there are two types of thalassaemias, the α-thalassaemia and ß-rithalassaemia found in the world population and they are mainly distributed around the Middle-East and South-East-Asia. The area is called the thalassaemic-belt (WHO, 1983). In conjunction with the thalassaemia, other hereditary blood disorders, such as Hb-E is also distributed widely in South-East-Asia. The αº-thalassaemia it self consists of a αº-thalassaemia and α+-thalassaemia. Product of marriage of couple bearing the αº-thalassaemia may result in the inheritance of Hb-Bart's hydrops feotalis, which was delivered as still birth or baby died soon after birth. Marriage between α-thalassaemia and α+-thalassaemia couple may result in the birth of babies with Hb-H disease. So far, the incidence of αº-thalassaemia in Indonesia especially in Medan has not well been investigated. Therefore, some problems need to be clarified, such as : (1) what is the prevalence of α-thalassaemia carriers among the ethnic groups in Medan, (2) does the_SEA deletion exist among the ethnic population in Medan and it's the distribution pattern, and (3) whether the occurrence of the-SEA deletion relates to a certain ethnic group. To answer these questions, a study has been carried out which covered 1.521 blood samples that represent ethnic groups in Medan which are Bataks, Chineses, Javaneses, Minangkabau, Malays, Acehneses and Niases (SP 2000) Medan. The study included tests to screen α-thalassaemia and α-thalassaemia carriers that carried out in the Clinical Pathology Laboratory Adam Malik Hospital and Gleneagles Hospital. in Medan, Indonesia. DNA analysis of αº-thalassaemia of SEA was performed in the Molecular Genetics Unit of the Kajidarah IMR Kuala Lumpur, Malaysia. From all samples, 117 were found to be hypochromic and microcytic and distributed here in : Bataks 503 (33.07%), Javaneses 466 (30.64%), Chineses 223 (14.66%), Malays 136 (8.94%), Minangkabau 128 (8.42%), Acehneses 57 (3.75%) and Niases 8 (0.53%). From all hypochromic, microcytic, peripheral blood films were made and the samples were also tested for the iron status to exclude the iron deficiency anaemia, HbA2 to discriminate the α-thalassaemia, from α-thalassaemia carriers. All the α-thalassaemia carriers underwent tests for inclusion bodies and molecular analysis using the PCR technique for _SEA mutant. From the overall investigation, it can be concluded that out of 1.521 blood samples tested, 117 samples which were classified as thalassaemia carriers (7.68% of the total study population), 51 (3.35%) are detected as α-thalassaemia carriers, 62 (4.07%) as α-thalassaemia carriers, and 4 (0.26%) as Hb-E carriers. Twenty six (26) out of 51 ?-thalassaemia carriers were tested for inclusion bodies and 18 (69.23%) prove to be positive, which means there were --SEA mutant. The rest 25 cases showed positive test in 5 cases. The molecular analysis performed on the αº-thalassaemia carriers showed that 26 (50.9%) have gene __SEA deletion or 1.7% with the estimation ranged from 1.1% to 2,3% of the tested population, The other 25 (48.1%) may have other mutations either of the αº-thalassaemia or α+-thalassaemia, or 1.64% with the estimation ranged from 1,04% to 2.24%. The prevalence of the gene SEA mutant are Malays 2.94%, Chinesee 2.69%, Javaneses 1.11%, Bataks 1,19%, Acehneses 3.50%, whilst none was found in the Minangkabaus and the Niases.

Ada dua jenis thalassemia yaitu thalassemia-αº dan thalassemia-ß pada berbagai populasi di dunia dengan pusat sebaran sekitar Laut Tengah, Timur Tengah, dan Asia Tenggara yang sering disebut sebagai sabuk thalassemia (WHO, 1983). Seperti halnya thalassemia, kelainan darah herediter yang lain yaitu HbE juga tersebar secara luas di Asia Tenggara. Thalassemia-α. terdiri atas thalassemia-α° dan tnalassemia-α+. Perkawinan dari pasangan thalassemia-α° dapat mewariskan keturunan Hb Bart's hydrop fetalis, bayi mati dalam kandungan, atau bayi lahir mati. Perkawinan antara thalassemia-α° dan thaiassernia-α+ dapat mewariskan keturunan penyakit HbH. Keberadaan carrier thalassemia-α. khususnya thalassemia-α° di Indonesia masih kurang dicermati terutama di Medan. Beberapa rnasalah utama yang perlu diajukan adalah (1) bagaimana prevalensi carder thalassemia-α. pada berbagai kelompok suku di Medan (2) apakah gen delesi_SEA terdapat pada berbagai suku di Medan dan bagaimana pola disrribusinya, dan (3) apakah keberadaan gen delesi _SEA terkait dengan kelompok suku tertentu Untuk menjawab pertanyaan tersebut telah dilakukan serangkaian penelitian pada 1.521 sarnpel darah yang mewakili kelompok suku yang terdapat di kota Medan yaitu 503 orang suku Batak (33,07%), 466 orang suku Jawa (30,64%), 223 orang suku Cina (14,66%), 136 orang suku Melayu(8,94%), 128 orang suku Minangkabau (8,42%), 57 orang suku Aceh (3,75%), dan 8 orang suku Nias (0,53%). Persentase suku sampel penelitian relatif sama dengan persentase suku hasil SP 2000 Medan. Penelitian meliputi skrining carrier thalassemia-α dan thalassernia-ß yang dikerjakan di Laboratorium Patologi Klinik Rumah Sakit Umum H. Adam Malik dan Rumah Sakit Gleneagles di Medan, Indonesia. Analisis DNA thalassemia-α° dengan mutasi deiesi _SEA dikerjakan di Unit Genetik Molekul Sahagian Kajidarah IMR Kuala Lumpur Malaysia. Pada semua sampel telah dilakukan skrining indeks hematologis untuk mendapatkan sampef mikrositer hipokrom. Kemudian, dilakukan pemeriksaan hapusan darah tepi dan status besi untuk menyingkirkan keberadaan anemia defisiensi besi. Kadar HbA2 ditentukan secara kuantitatif untuk membedakan carrier thalassemia-α dan thatassernia-ß (3. Selanjutnya, pada semua sampel carrier thalassemia-α diperiksa badan inklusi dan analisis molekular dengan teknik PCR untuk mutan_SEA Dari 1.521 sampel yang diperiksa ditemukan 117 (7,68%) carrier thalassemia yang di antaranya sebanyak 51 (3,35%) carrier thalassemia-α, 62 (4,07%) carrier thalassemia-ß. dan 4 (0,26%) carrier HbE. Pemeriksaan badan inklusi pada carrier thalassemia-α ditemukan hanya 18 (69,23%) dari 26 sampel mutan __SEA dan 5 (20 %) dari 25 sampel nonmutan __SEA. Analisis molekular menunjukkan bahwa 26 (50,9%) mengalami delesi __SEA yaitu 1,7% dari seluruh populasi yang diteliti dengan estimasi antara 1,1% hingga 2,3%, sedangkan 25 (48,1 %) diduga mempunyai mutasi lain baik penyebab thalassemia-α+ maupun α+ yaitu 1,64% dengan estimasi antara 1,04% hingga 24%. Prevalensi gen mutan __SEA dijumpai pada suku Melayu 2,94%, Cina 2,69%, Jawa 1,71%, Batak 1,19%, Aceh 3,50% dan tidak dijumpai pada suku Minangkabau dan Nias.