Carrier screening and genetic counselling in beta-thalassemia.

This paper review the most important aspects of carrier detection procedures, genetic counselling, population screening and prenatal diagnosis of beta-thalassemias. Carrier detection can be made retrospectively, following the birth of an affected child or prospectively. Several programmes, with the aim of preventing homozygous beta-thalassemia, based on carrier screening and counselling of couples at marriage; preconception or early pregnancy, are operating in several Mediterranean at-risk populations. These programmes have been very effective, as indicated by increasing knowledge on thalassemia and its prevention by the target population and by the marked decline of the incidence of thalassemia major. Carrier detection is carried out by haematological methods followed by mutation detection by DNA analysis. Prenatal diagnosis is accomplished by mutation analysis on PCR-amplified DNA from chorionic villi. Future prospects include automation of the process of mutation-detection, simplification of preconception and preimplantation diagnosis and fetal diagnosis by analysis of fetal cells in maternal circulation.