Prenatal diagnosis in beta-thalassemia: an Indian experience.

OBJECTIVES

Thalassemia is the most common single gene disorder and is widely distributed in Asian Indians with an average prevalence rate of 4%, with a high prevalence among Sindhis, Punjabis, Gujratis and Bengalis. Prevention and control of beta-thalassemia disease require the accurate diagnosis of carriers and proper genetic counseling.

METHOD

Prenatal diagnosis can be performed in the first or second trimester of pregnancy by DNA analysis using polymerase chain reaction. Since there are 17 mutations as well as rare ones causing beta-thalassemia in Asian Indians, the point mutation detection by reverse dot blot (RDB) allele-specific oligonucleotide hybridization for common mutations along with the amplification refractory mutation system (ARMS) technique was developed for prenatal diagnosis. Maternal contamination of fetal DNA was ruled out by the variable number of tandem repeat analysis using apolipoprotein B site.

RESULTS

Using both techniques (RDB and ARMS) we were able to offer complete diagnosis in 53 pregnancies. On molecular analysis 23% were found to be normal, 48.0% were carriers, and 29.0% were affected with beta-thalassemia. Parents were counseled to continue the pregnancy when the fetuses were either normal or had traits whereas in the case of an affected fetus, the parents opted for termination of the pregnancy.

CONCLUSION

Prenatal diagnosis of beta-thalassemia by the RDB or ARMS technique can prevent the birth of an affected child in developing countries in which beta-thalassemia is quite prevalent.