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 alpha degrees -thalassaemia (south-east Asian type deletion). Primers and TaqMan probes were designed to specifically amplify an alpha degrees -thal chromosomal fragment or a normal alpha -chromosomal fragment. Variations in input target DNA in individual sample wells were normalized by the simultaneous amplification of a beta -actin gene fragment and results expressed as a ratio to that of beta -actin. There was no overlap of the data between the homozygous alpha degrees -thal, alpha degrees -thal and normal subjects. Up to 5% maternal DNA (alpha degrees -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 alpha -genes.