Challenges in prenatal diagnosis of beta thalassaemia: couples with normal HbA2 in one partner

Objectives To undertake beta-genotyping in couples having normal/borderline HbA(2) levels in one partner to offer the possibility of prenatal diagnosis of thalassaemia. Methods A total of 967 couples were screened for beta-thalassaemia. Haematological analysis was carried out on a Sysmex K-1000 analyser. The HbA(2) and HbF levels were measured by High Performance Liquid Chromatography-Variant II analyser (Bio-Rad, USA). beta-globin gene analysis was done by reverse dot blot hybridization, amplification refractory mutation system or DNA sequencing. Alpha globin gene triplication was determined by Multiplex PCR. Results In 33 of 967 couples, one partner had a normal/borderline HbA(2)level (1-3.5%); however a beta-thalassaemia mutation could be identified in 24 of these individuals. Molecular analysis of the beta-globin gene revealed the presence of the capsite + 1 (A -> C) [HBB: c.-50 A -> C] mutation in 15 cases (60%), Poly A(T -> C) [HBB: c.* 110 T -> C] mutation in two cases (8%), IVS 1-5 (G -> C) [HBB: c. 92 + 5 (G -> C)] mutation in four cases (17%) and the CD 15 (G -> A) [HBB: c. 47 G -> A] mutation, CD 16 (-C) [HBB: c. 51 del C] mutation and CD 30 (G -> C) [HBB: c. 93 G -> C] mutation in one case each (4%). Alpha gene triplication was found in five cases, while four cases remained uncharacterized. Conclusions beta-genotyping should always be done in a couple if one partner is a beta-thalassaemia carrier irrespective of the RBC indices and HbA(2) levels of the other partner. (C) 2015 John Wiley & Sons, Ltd.