[Successful preimplantation genetic diagnosis for alpha-thalassemia using fluorescent polymerase chain reaction].

Objective: To develop single-cell fluorescent gap polymerase chain reaction (PCR) assay for preimplantation genetic diagnosis (PGD) in couples at risk of having child with alpha-thalassemia.

Methods: Single cell fluorescent gap PCR which can detect the alpha-thalassemia Southeast Asia deletion (-SEA deletion), was applied to single lymphocytes and blastomeres which coming from four clinical PGD cycles.

Results: The Single cell fluorescent gap PCR can detect the alpha-thalassemia -SEA deletion, which account for 94% of hydrop fetalis in Chinese population with an amplification efficiency of 90.0% (72/80) and allele drop-out (ADO) rate of 8.3% (6/72) in lymphocytes. In four clinical PGD cycles, a total 38 embryos were detected and 38 blastomeres were obtained. Thirty-four blastomeres were amplified with the amplification efficiency of 89.5% (34/38) and ADO rate of 5.9% (2/34). Eleven embryos were shown to be normal homozygous, eight embryos were shown to be heterozygous and 15 embryos were shown to be affected homozygous. Eleven embryos were transferred back to the uterus of the patients. Two pregnancy achieved, resulting in two live healthy births, which confirmed the results of PGD.

Conclusion: This first reported unaffected pregnancy resulting from PGD using fluorescent gap PCR for alpha-thalassemia demonstrates that this technique, as an alternative to prenatal diagnosis, is a reliable and effective way to help those carrier couples to get a healthy baby.