Heterogeneity in α-thalassemia interactions in Malays, Chinese and Indians in Malaysia

Aim: Interactions between different determinants of alpha-thalassemia raises considerable problems, particularly during pregnancies where antenatal diagnosis is necessary. This study aims to determine the different types of deletional alpha-thalassemia and Hemoglobin Constant Spring (HbCS), and their frequency in Malays, Chinese and Indians in Malaysia. Methods: DNA from 650 pregnant women from the Antenatal Clinic of the University of Malaya Medical Center in Kuala Lumpur, Malaysia who showed mean cell volume <= 89 fL and/or mean cell hemoglobin <= 28 pg were analyzed for the double alpha-globin gene South-East Asian deletion (--(SEA)), the -alpha(3.7) and -alpha(4.2) single alpha-globin gene deletions and HbCS. Results: One hundred and three (15.8%) of the pregnant women were confirmed as alpha-thalassemia carriers: 25 (3.8%) were alpha-thalassemia-1 carriers with the --(SEA)/alpha alpha genotype, 64 (9.8%) were heterozygous for the -alpha(3.7) rightward deletion (-alpha(3.7)/alpha alpha), four (0.6%) were heterozygous for the -alpha(4.2) leftward deletion (-alpha(4.2)/alpha alpha), nine (1.4%) were heterozygous for HbCS (alpha(CS)alpha/alpha alpha) and one (0.2%) was compound heterozygous with the -alpha(3.7)/alpha(CS)alpha genotype. The double alpha-globin gene --(SEA) deletion was significantly higher in the Chinese (15%) compared to the Malays (2.5%) and not detected in the Indians studied. The -alpha(3.7) deletion was distributed equally in the three races. HbCS and -alpha(4.2) was observed only in the Malays. Conclusion: The data obtained gives a better understanding of the interactions of the different alpha-thalassemia determinants in the different ethnic groups, thus enabling more rapid and specific confirmation of alpha-thalassemia in affected pregnancies where antenatal diagnosis is necessary.