PREVALENCE AND MUTATIONS OF β-THALASSEMIA TRAIT AND ABNORMAL HEMOGLOBINS IN PREMARITAL SCREENING IN ÇANAKKALE PROVINCE, TURKEY
Uludağ A, Uysal A, Uludağ A, Ertekin YH, Tekin M, Kütük B, Sılan F, Özdemir Ö
*Corresponding Author: Associate Professor Ahmet Uysal, Department of Obstetrics and Gynecology, Çanakkale Onsekiz Mart University, Terzioglu Yerleskesi 17100, Çanakkale, Turkey. Tel: +90-533-263- 5540. Fax: +90-028-626-3597. E-mail: drahmetuysal@hotmail.com
page: 29

DISCUSSION

β-Thalassemia is a well-known genetic disorder of the globin gene, with a worldwide distribution. The Ministry of Health and the Turkish National Hemoglobinopathies Council (MH and TNHC) reported a 4.3% prevalence of β-thal trait in a population of 377,399 healthy subjects from 16 cities in Turkey [6]. However, no study has reported the prevalence of β-thal trait and abnormal Hbs for the province of Çanakkale until now. Çanakkale is located in the far west of Turkey between the Marmara and Aegean regions. Different to other areas of Turkey, the majority of the population is comprised of immigrants from Balkan countries and Romania. The sociocultural level of the city is above Turkey average. Our study is the first to report these data, save for our preliminary premarital screening report of 1.45% limited to the city of Çanakkale alone. This rate was 0.06% for Hb S (HBB: c.20A>T) carriers. This prevalence of β-thal carriers in the province is not high compared to the prevalence in Turkey as a whole. In İzmir (in the Aegean region of Turkey), the neighboring provinces of Çanakkale, the prevalence of β-thal and Hb S were 4.96 and 0.13%, respectively [3]. In Turkey, 36 different β-thal mutations have been described to date. The most commonly identified mutations are, in order, HBB: c.93-21G>A, HBB: c.92+6T>C [IVS-I-6 (T>C)] and HBB: c.25_26delAA [codon 8 (‒AA)] [2]. In the Mediterranean region, 19 different mutations have been reported and the most frequently observed are HBB: c.93-21G>A, HBB: c.92+6T>C and HBB: c.-80T>A [‒30 (T>A)] mutations. The same study reported the Hb S incidence as 10.3% [7]. This wide molecular variety, the molecular genetic description of the disease, significantly hampers strategies and programs to prevent the disease. In our region, according to the β-globin genetic analysis we conducted, there were 14 different mutations identified in carriers of β-thal. The most frequently observed mutation for β-thal in Turkey with a rate of about 40.0% is reported as HBB: c.93-21G>A [2]. In our study, this mutation has the highest frequency of 26.08%, lower than the average for Turkey and different to a range of regions in Turkey [2,7-9]. The frequency of HBB: c.93-21G>A in β-thal mutations exceeds 50.0% in Central Anatolia, but falls to 25.0% in East and Southeast Anatolia [2,10,11]. Keser et al. [8] calculated the frequency of HBB: c.93-21G>A as 35.6% in the Antalya region in their 2004 study. The same mutation was reported as 49.02% in the Central Anatolia region by Beksaç et al. [9,11]. Interestingly, although there are so many immigrants in Çanakkale from the Balkans, who came during the Balkan War (1912), the mutation profile is different from Balkan countries, especially Romania [12]. Selected marriages because of cultural differences in those days may cause this difference. As seen in our study, β-thal is an important health problem in Turkey. As there is no certain treatment of β-thal, it is very important to determine the mutations and the carriers for preventing the disease. For correct genetic counseling it is necessary to know the exact mutations within the families. The couple both found to be β-thal carriers in our study did not have genetic counseling so they had lost their first child because of β-TM. Prenatal diagnosis by amniocentesis of the fetus for their second pregnancy was found to be homozygous for a normal β-globin gene. This dramatic family history emphasizes the importance of prenatal screening, especially for carriers. The wide heterogeneity of β-thal at a molecular level is an important barrier to diagnosis and prevention of the disease. This is the first report on the frequency and mutation profiles of β-thal for Çanakkale. The incidence of β-thal carriers in Çanakkale is below the average of Turkey. A high level of sociocultural population and low rates of consanguineous marriages could cause this. The most frequently observed mutation profile and rate of β-thal in our region is different to the mutation profiles and rates observed in different regions of Turkey. To prevent an increase in β-thal incidence and ensure families become parents of healthy children, it is necessary to increase consanguinity marriage education, genetic counseling before pregnancy and prenatal genetic screening programs. Declaration of Interest. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.



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