Genotype of subjects with borderline hemoglobin A2 levels: implication for beta-thalassemia carrier screening.

In this study, we have defined by molecular analysis, the alpha, beta, and delta globin genotype in a group of individuals with normal or thal-like red cell indices but borderline hemoglobin (Hb)A2 levels, who were identified in a program for beta-thal carrier screening. In 37 of 125 individuals with borderline HbA2 levels, we detected a molecular defect in the beta, in both the delta and the beta, or in the alpha globin gene. Specifically seven of these subjects were carriers of the -101 C T mutation, ten of the IVSI nt6 T C mutation, 16 were double heterozygotes for delta and beta thal, and two had the triple alpha globin gene and two the single alpha globin gene deletion. From these results, we may conclude that subjects with borderline HbA2, particularly when they marry a typical beta-thal carrier, should be extensively investigated in order not to miss heterozygous beta-thalassemia.