Quantitative polmerase chain reaction for the rapid prenatal diagnosis of homozygous α-thalassaemia (Hb Barts hydrops fetalis)
A quantitative polymerase chain reaction (Q-PCR) method based on the TaqMan technology has been devised for the prenatal diagnosis of homozygous α°−thalassaemia (south-east Asian type deletion). Primers and TaqMan probes were designed to specifically amplify an α°-thal chromosomal fragment or a normal α-chromosomal fragment. Variations in input target DNA in individual sample wells were normalized by the simultaneous amplification of a β-actin gene fragment and results expressed as a ratio to that of β-actin. There was no overlap of the data between the homozygous α°-thal, α°-thal and normal subjects. Up to 5% maternal DNA (α°-thal) contamination did not affect the specificity of the result. In 31 prenatal diagnoses, the result using Q-PCR compared favourably with the gold standard of Southern hybridization of α-genes.