Prenatal diagnosis of beta-thalassaemia by reverse dot-blot hybridization

Thalassaemia is the most common genetic disease and is a public health prob lem of Thailand. Prevention and control of beta-thalassaemia diseases need accurate diagnosis of carriers and proper genetic counselling. Prenatal dia gnosis is needed to prevent birth of the thalassaemic offspring in the coup le at risk. This can be performed in the first trimester of pregnancy by DN A analysis using the polymerase chain reaction (PCR). Since there are more than 20 mutations causing beta-thalassaemia in Thailand, the point mutation detection by reverse dot-blot allele-specific oligonucleotide (ASO) hybrid ization was developed using two sets of ASO probes. The first battery of AS O probes has been designed to detect 10 common beta-globin gene mutations i ncluding codon 26; G --> A (Hb E); codons 41/42, -TCTT; codon 17, A --> T; IVS 2 nt 654, C --> T; IVS 1 nt 1, G --> T; IVS 1 nt 5, G --> C; codon 19, A --> G (Hb Malay); codon 35, C --> A; codons 71/72, +A and -28 ATA, A --> G. The second set of ASO probes detect 14 uncommon beta-thalassaemia mutati ons. We applied this reverse dot-blot hybridization technique to perform prenata l diagnosis in 105 pregnancies at risk of having severe beta-thalassaemia d iseases. 36 fetuses (34 per cent) were found to be affected with homozygous P-thalassaemia or beta-thalassaemia/Hb E disease in which one was twin pre gnancy. The others included 31 fetuses with heterozygous beta-thalassaemia, 22 heterozygous Hb E, 1 homozygous Hb E and 16 normal fetuses. The common set of ASO probes detected about 95 per cent of cases which suggests that p renatal diagnosis for beta-thalassaemia disease can be easily carried out b y this approach. Copyright (C) 1999 John Wiley & Sons, Ltd.