Characterization of the molecular defect of
beta-thalassemia in Thais has enabled us to establish prenatal diagnosis for homozygous
beta-thalassemia and
beta-thalassemia/Hb E. The nature of the
beta-thalassemia mutation of each high risk couple or of the previous affected child was firstly identified after counseling. Detection of
beta-thalassemia mutations was performed by dot-blot hybridization of the amplified
DNA with a set of HRP-labeled ASO-probes specific for the common mutations. If the mutation could be characterized, prenatal diagnosis (PND) would be performed by using
DNA extracted either from the chorionic villi (CVS) or amniotic fluid fibroblast in the first trimester of pregnancy or from fetal blood in the second trimester.
DNA analysis was carried out in 23 couples at risk of having homozygous
beta-thalassemia and 88 couples at risk for
beta-thalassemia/Hb E. However, PND was performed by this technique in 22 pregnancies from 21 couples at risk of having homozygous
beta-thalassemia children and 86 pregnancies from 71 couples at risk for
beta-thalassemia/Hb E; 9 couples underwent more than one prenatal diagnosis. The results showed that, although there are more than 20
beta-thalassemia mutations in the Thai population, PND by
DNA analysis could be carried out in more than 95% of the risk couples by using beta(E) and 10 different HRP-labeled ASO probes. This technique was simple, economic and avoided the use of
radioactive isotope.