Reproducibility of different aneuploid findings at second trophectoderm biopsy evaluated by independent NGS platforms

• Published in: Reproductive biomedicine online 2019-04, Vol.38, p.e17-e17
• Main Authors: Horak, Jakub, Kubicek, David, Navratil, Rostislav, Hornak, Miroslav, Janickova, Nada, Tauwinklova, Gabriela, Vesela, Katerina
• Format: Article
• Language: English
• Subjects: mosaicism; PG-Seq; PGT-A; segmental aneuploidy; sub-chromosomal variation
• ISSN: 1472-6483; 1472-6491
• DOI: 10.1016/j.rbmo.2019.03.030

Preimplantation genetic testing of aneuploidies (PGT-A) enables the selection of euploid embryos in order to increase implantation rates and reduce miscarriage rates after embryo transfer. Next Generation Sequencing (NGS) platforms provide higher dynamic range than other methods and are validated for the detection of copy number variations starting at 20% mosaicism. Sub-chromosomal segmental aneuploidies above 15 MBp are reported in routine PGT-A, and the resolution can be increased to 1-2 MBp when PGT targeted to a previously described structural rearrangement is carried out (PGT-SR). While calling whole chromosomal aneuploidy leads to the elimination of clearly non- viable embryos from transfer to the uterus, numerous healthy live-births have been reported after transferring mosaic embryos. Clinical impact of segmental aneuploidies detected in trophectoderm biopsies remains unclear. All embryos were biopsied at day 5/6 and trophectoderm samples were analyzed by VeriSeq™ PGS Kit (Illumina). Discarded embryos dedicated to research with the consent of patients were de-vitrified and after blastocyst re-expansion a second trophectoderm sample of the same size was biopsied for analysis using the PG-Seq™ platform (RHS). In total, 95 embryos were re- analyzed and the results of both replicates were compared. After the first PGT-A, 73 embryos were classified aneuploid, 12 mosaic, and 10 euploid. Assessing the same set of samples by aberration type, 63 whole chromosomal aneuploidies were originally called using VeriSeq™, 28 whole chromosomal mosaics, 36 segmental aneuploidies and 9 segmental aneuploidy mosaics. Reproducibility of various aneuploidy types was evaluated after second biopsy analysis using PG-Seq™. In the group of 10 euploid embryos, the original status was confirmed in 9 embryos with one rebiopsied sample reporting a mosaic loss of chromosome 17. Aneuploidy was concordant in 63 out of 73 samples with 9/10 of the non-concordant results changing from segmental aneuploidy to euploid. Only 3 of 12 mosaic embryos remained mosaic with 6 rebiopsied mosaic embryos turning to euploid and 3 aneuploid. When evaluating each chromosomal change separately, reproducibility of 96.8% was observed for whole chromosomal aneuploidies (61/63), 50% for segmentals (18/36) and only 10.8% for mosaics (4/37). Particularly, none of the 9 segmental mosaics were detected in the second biopsy. In contrast to this, second biopsy testing revealed 2 whole chromosomal aneuploidies, 8