Prenatal diagnosis of the thalassaemia syndromes by rapid DNA analytical methods

Prenatal diagnostic strategies applied today are based mainly on polymerase chain reaction (PCR) analytical protocols. In Greece a wide range of mutations underlie the thalassaemic haemoglobinopathies, and consequently a variety of PCR-based methods are required to facilitate diagnosis of all potential abnormal genotypes. PCR protocols include those which are relatively simple and others that are technically challenging, but very few have been designed for high through-put clinical diagnostics. Over a period of 18 months we carried out prenatal diagnosis of 147 pregnancies (150 fetal samples) at risk for a wide range of haemoglobinopathies. This involved the precise characterization of parental genotypes and the subsequent analysis of fetal DNA samples. In this series, 18 different mutations in the alpha- or beta-globin clusters were identified. For the characterization of these mutations, five PCR-based protocols were selected: denaturing gradient gel electrophoresis (DGGE), amplification refractory mutation system (ARMS) PCR, restriction endonuclease analysis of PCR fragments, oligonucleotide hybridization and 'gap' PCR for detection of deletions. To avoid spurious diagnosis due to contamination of fetal samples, two additional methods were used to genotype polymorphic variable nucleotide tandem repeat (VNTR) regions of the genome in parental and fetal samples. Through analysis of the results we assess the advantages and drawbacks of the selected PCR-based protocols for providing routine clinical diagnostics.