Prenatal diagnosis and control strategies for beta-thalassaemia on the Indian subcontinent.

BACKGROUND: The control of beta-thalassaemia by prenatal diagnosis is an important option in India. The disease is common and resources are scarce for the treatment of affected children. Presently the most suitable approach for prenatal diagnosis is DNA analysis of a chorion villus sample by direct mutation detection. For the implementation of such a prenatal diagnosis programme it is essential to know the spectrum of beta-thalassaemia mutations in the population. METHOD: The beta-thalassaemia mutations of 708 unrelated carriers from seven different regions of the Indian subcontinent were characterized by the allele-specific polymerase chain reaction and DNA sequencing. RESULTS: Sixteen different beta-thalassaemia mutations were identified which could be divided into three groups according to their frequencies. Five common mutations accounted for 93% of alleles. Significant regional differences in the frequency and distribution of mutations were observed. CONCLUSIONS: The spectrum of mutations defined forms the basis for a beta-thalassaemia prenatal diagnosis programme in India. A strategy has been outlined for mutation detection which could be successfully applied. Since prenatal diagnosis has become comparatively simple, recommendations are made for a community-based thalassaemia control programme.