Hb E - alpha - thalassemia at Maharaj Nakhon Si Thammarat hospital

ABSTRACT

Both hemoglobin E (Hb E) and a-thalassemia are prevalence in Thailand. Hb E-a-thalassemia syndromes are therefore common. Individuals with these syndromes are at risk for both a- and b-thalassemia diseases. In this study, the prevalence of Hb E-a-thalassemia was examined on 204 Southern Thai subjects who were encountered at the Maharaj Nakhon Si Thammarat hospital. The a-thalassemia determinants examined using PCR methods included a-thalassemia 1 (SEA type), a-thalassemia 2 (3.7 kb and 4.2 kb deletions) and Hb Constant Spring gene (aCS). Hb E gene (bE) was confirmed in all cases using allele specific PCR. The prevalence of a-thalassemia 1, a-thalassemia 2 and aCS in  this Thai  population  were found to be 2.0 %, 15.7 % and 3.9 %,  respectively. As many as 11 Hb E genotypes were observed; 71.1 % heterozygous Hb E, 1.5 % heterozygous Hb E with heterozygous a-thalassemia 1, 10.3 %  hetetozygous Hb E with  heterozygous a-thalassemia 2 (3.7 kb), 1.5 % heterozygous Hb E with  heterozygous a-thalassemia 2 (4.2 kb), 2.9 % heterozygous Hb E with heterozygous aCS, 0.5 %  heterozygous Hb E with homozygous a-thalassemia 2, 1.0 % heterozygous Hb E with compound  heterozygous a-thalassemia 2 and aCS, 6.8 % homozygous Hb E, 0.5 % homozygous Hb E with  heterozygous a-thalassemia 1, 2.4 % homozygous Hb E with  heterozygous a-thalassemia 2 and 1.5 % b-thalassemia / Hb E disease. It was found that using hematological data alone it is very difficult to differentiate all these genotypes. It is therefore recommended for those with Hb E, whose couples are carriers of a-thalassemia 1, to be examined for a-thalassemia 1 especially when the level of Hb E is less than 25 % in order to prevent the Hb Bart’s hydrops fetalis and provide appropriate genetic counseling.