60. FOUR YEARS EXPERIENCE OF PREIMPLANTATION GENETIC TESTING OF FOUR MONOGENIC DISORDERS (CYSTIC FIBROSIS, BETA-THALASSAEMIA, HEMOPHILIA A AND B)

Abstract

Introduction Preimplantation genetic testing (PGT) is a significant challenge and a widely established reproductive alternative for couples with high-risk of transmitting an inherited monogenic disorder. In this study, we report single centre PGT experience at the Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico of Milan, Italy, from 2015 to 2018 after the ruling of the Italian Constitutional Court (96/2015) which legalized embryo genetic analysis in couples with high genetic risk for the first time in Italy. Four diseases were firstly considered: cystic fibrosis and beta-thalassaemia, as autosomal recessive disorders, and hemophilia A and B, as X-linked disorders. Material & methods Pre-clinical PGT workup was performed for 124 couples after genetic counselling. Thirty-one underwent PGD cycles for cystic fibrosis, 41 for beta-thalassemia and 3 couples for hemophilia A and 1 for hemophilia B. In vitro fertilization (IVF) procedures were used to generate embryos in vitro by intracytoplasmic sperm injection (ICSI). Blastocysts at day 5-7 were biopsied and vitrified post biopsy. Informative short tandem repeat (STR) markers were used for linkage analysis alone or in combination with family gene mutation detection by multiplex PCR. Following diagnosis, embryos with no gene mutation were transferred. Results Two hundred and forty-seven embryos were obtained. Blastocyst biopsy was performed on 236 day 5-7 embryos. Successful genetic results were obtained in 195 embryos (83%), 121 of those were diagnosed unaffected (62%) and genetically transferable. No conclusive diagnosis was obtained for 41 biopsies and 15 embryos were rebiopsied. Transfer of 84 cryopreserved embryos resulted in 46 pregnancy with an implantation rate of 55% per embryo transfer (ET). Pregnancies result in 26 live births and 8 miscarriages. Thirty-six embryos still remain cryopreserved. Fourteen couples underwent prenatal diagnosis and results were consistent with PGT genetic analysis. Parameters such as allele drop-out, contamination and recombination were considered to evaluate diagnostic accuracy and reliability of genetic testing. Our data showed an allele drop-out rate of 5%, amplification failure of 10% and recombination rate of 6%. Conclusions Our four years’ experience on PGT demonstrates that couples with high risks of transmitting genetic mutations that cause severe medical conditions can really benefit from PGT technique, as it represents a robust reproductive option preventing abortion of an affected pregnancy with great suffering to the pair. Our PGT positive experience serves as an incentive for the use of this procedure in other genetic diseases in our centre.