PRENATAL-DIAGNOSIS OF BETA-THALASSEMIA AND SICKLE-CELL-ANEMIA IN TURKEY

This paper reports our experience of molecular analysis and diagnosis of beta-thalassaemia and sickle cell anaemia (HbS) in 70 prospective p arents of Turkish descent and their fetuses. Molecular screening was c arried out by allele-specific oligonucleotide (ASO) hybridization of a mplified DNA to the 12 most common mutations in the Turkish population . By using this approach, we were able to define the mutation in 95 pe r cent of chromosomes investigated. Genomic sequencing led to the addi tional detection of three rare mutations: Cd 44 (- C), IVS-I-5 (G-C), and IVS-I-116 (T-G). All diagnoses were successfully accomplished and no misdiagnosis occurred. Consanguineous marriage appears to contribut e significantly to the frequency of affected births in Turkey. Out of the 14 homozygous fetuses, six were the result of close consanguinity. This study indicates that fetal diagnosis of P-thalassaemia and HbS m ay be obtained in practically all cases, even in a heterogeneous popul ation like the Turkish population, when early methods of fetal samplin g are combined with polymerase chain reaction (PCR)-based techniques. Until gene therapy becomes a reality, the only approaches to the contr ol of haemoglobinopathies are prevention and avoidance. The most relev ant and common aspects of the programmes, which have been very effecti ve in reducing the birth rate of beta-thalassaemia major in several at -risk areas of the Mediterranean basin, are the continuous educational campaigns directed at the population at large, the voluntary basis, a nd non-directive counseling. The most important challenge for the erad ication of the haemoglobin-opathies in Turkey is the organization of a nation-wide and comprehensive genetic preventive programme based on D NA technology.