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Frequency of β-Thalassemia or β-Hemoglobinopathy Carriers Simultaneously Affected with α-Thalassemia in Iran by Shaban Alizadeh, Mahsa Shanaki Bavarsad, Akbar Dorgalaleh, Zahra Kashani Khatib, Hossein Dargahi, Nhaid Nassiri, Fatemeh Hamid, Fakher Rahim, Kaveh Jaseb, Najmaldin Saki

Background: β-thalassemias are prevalent heritable single gene disorders affecting the quantity of the hemoglobin molecule. Rarely, a co-inheritance of these impairments with α-thalassemia and/or a hemoglobinopathy occurs and makes an important double heterozygote or homozygous state. Thus finding these cases is essential for genetic counseling. The present study aimed to identify the prevalence of coexistent α-thalassemia mutations, hemoglobinopathies, and β-thalassemia determinants.
Methods: This descriptive study was performed on 5760 patients. We used complete blood cell count, Hb electrophoresis, and HbA2 measurement for thalassemia carrier identification. Increased HbA2 (≥ 3.5%) is the standard diagnostic marker for β-thalassemia, while normal HbA2 with low MCH and MCV can indicate an α-thalassemia carrier or atypical β-thalassemia minor. Individuals with MCV ˂ 80 fL, MCH ˂ 27 pg, and hemoglobin ≤ 15.3 g/dL in men or ≤ 14 g/dL in women, were candidates for molecular thalassemia investigations. Patients with abnormal hemoglobin varieties in hemoglobin electrophoresis were referred to a genetics laboratory for hemoglobinopathy detection.
Results: 141 subjects out of 5760 were affected by α and β-thalassemia or a β-hemoglobinopathy simultaneously, including: 13 (11.1%) fetuses, 55 (38.2%) male cases, and 73 (50.7%) females. Among these 141 α-thalassemia patients, 92 cases (65.24% ) were β-thalassemia carriers and 3 (2.12% ) were β-thalassemia major, 43(30.49%) had β-hemoglobinopathies, and 3 cases (2.12%) had co-inherited β-thalassemia and variant hemoglobins. 31 β-gene mutations were observed in this population, the most common being HbS Cd6 (A > T) ( 24%). These thalassemia determinants account for about 46% of all detected mutations. As for α-gene mutations, -3.7 detection was the most prevalent.
Conclusions: The relatively high prevalence of co-inherited α-thalassemia and hemoglobinopathies among β-thalassemia carriers indicates the importance of molecular analysis to diagnose these double heterozygous or sole homozygous cases for prenatal diagnostic purposes and putting forth strategies to prevent more complicated and dangerous combinations.

DOI: 10.7754/Clin.Lab.2013.130306