Distribution of thalassemias and associated hemoglobinopathies identified by prenatal diagnosis in Taiwan

Abstract

Background: Hemoglobin (Hb) gene disorders are common hereditary disorders in Taiwan, and α- and β-thalassemias are among the well-known Hb disorders here. Our study provides a primary reference for designing a locally relevant antenatal diagnostic test to control the spread of thalassemia.

Methods: Between 1998 and 2011, prenatal diagnoses for identifying thalassemia and hemoglobinopathies were performed on 1240 fetuses at risk for α-hydrops and β-thalassemia major.

Results: Of 1240 specimens analyzed, 1082 (87%) were obtained by amniocentesis; 125 (10%), by chorionic villus sampling; and 33 (3%), by cordocentesis. Prenatal diagnoses revealed that 21.5% of these fetuses as thalassemia major (including α-thalassemia hydrops, β-thalassemia major, and Hb E/β-thalassemia); 50.2%, for thalassemia minor (include α-thalassemia carrier, β-thalassemia carrier, and α-thalassemia combined β-thalassemia carrier); and 28.3% for normal type (include non-α, β-thalassemia). The most common α-hydrops were SEA (Southeast Asian) and Philippine type (frequencies of 74.91 and 5.24%, respectively). The frequency of the IVS-II-654 combined codons 41/42 mutation, the most common β-thalassemia major mutation in this region, was 5.24%. Two fetuses were found with E/β-thalassemia (HbE/IVS-II-654 and HbE/codons 41/42, respectively). Since 1993, Taiwan's Department of Health adopted a national program for screening pregnancies to control spread of thalassemia. In the last 10years, less than 3 such cases have occurred per year. After 2003, this number was 0 for a total of 4years (2003, 2004, 2007, and 2008).

Conclusion: In Taiwan, incidence and frequency of thalassemia genotypes were similar to those previously reported. The national program for screening pregnancies to control spread of thalassemia that resulted in a marked decline in the number of newborns with thalassemia major. Interestingly, prenatal diagnoses revealed 21.5% for thalassemia major, 50.2% for thalassemia minor, 28.3% normal comparison of thalassemia type distribution showed normal type increasing by 13.2% and major type decreasing by 14%. This unique and significant finding needs further clinical studies and discussion to explain such a phenomenon.

Keywords: ACRS; Amplification-created restriction site; Hb; Hb Constant Spring; Hb Quong Sze; HbCS; HbQS; Hemoglobinopathy; Molecular lesion; Prenatal diagnosis; RFLP; Restriction fragment length polymorphism; SEA; Southeast Asian; Thalassemia; VNTR; Variable number of tandem repeat; hemoglobin.