Incidence of Hb Barts and α-Thalassaemia Genotypes in a South African Population

Abstract
The cord blood of 1207 randomly selected neonates from the Cape Colored population of South Africa was analyzed for the presence of Hb Barts. Forty individuals (3.3%) had detectable Hb Barts levels with values ranging from 1.1-7.3%. Restriction enzyme analysis of DNA from subjects with Hb Barts showed that 85% of the cases studied had the genotypes - .alpha.3.7/.alpha..alpha. or -.alpha.3.7/.alpha.3.7. The observed frequency of the -.alpha./.alpha..alpha. genotype was much lower than the expected frequency which suggests that this genotype is often not associated with detectable levels of Hb Barts. Mapping of the .zeta.-globin locus in 3 subjects with HbH disease revealed the presence of the --SEA/.alpha.-thalassemia determinant in this population.