Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

Abstract

Preimplantation genetic diagnosis of aneuploidy (PGD-A) with comprehensive chromosome analysis has been known to improve pregnancy outcomes. Accuracy in detecting sex chromosomes becomes important when selecting against embryos at risk for sex-linked disorders. A total of 21,356 PGD-A cycles consisting of day-3 (cleavage) or day-5 (blastocyst) biopsies were received at the same laboratory for PGD-A via fluorescence in situ hybridization (FISH) or array comparative genome hybridization (aCGH) from multiple fertility centres. The misdiagnosis rates were 0.12% (Wilson 95% CI 0.05 to 0.25%) in day-3 FISH cycles, 0.48% (Wilson 95% CI 0.19 to 1.22%) in day-3 aCGH cycles and 0.0% (Wilson 95% CI 0 to 0.26) in day-5 aCGH cycles. Although rare, the likely causative biological event for true misdiagnosis is embryonic XX/XY mosaicism. Reanalysis of 1219 abnormal cleavage-stage research embryos revealed a 73% incidence of minor and major mosaicism. Only four (0.3%) embryos were found to be diploid and contained XX and XY cells that could potentially account for the misdiagnosis of sex. Our investigation identified errors leading to misdiagnosis and their attribution to specific events during PGD-A testing. The reported misdiagnosis rates suggest that PGD-A for sex determination is highly accurate, particularly when using aCGH applied to blastocyst biopsies.

High-efficiency derivation of human embryonic stem cell lines using a culture system with minimized trophoblast cell proliferation

“…However, this was not unprecedented as there was a report of deriving normal diploid hESCs from aneuploid embryos [ 48 ]. This may be due to a phenomenon called “mosaicism” found in small percentages of eight-cell-stage embryos at the time of PGD [ 49 ]. The meiotic nondisjunction occurring during germ cell formation and the mitotic nondisjunction occurring during the early cleavage stage of the embryos are mostly responsible for the mosaicism, resulting in affected embryos with both normal diploid cells and aneuploid cells [ 50 – 52 ] (Additional file 6 : Figure S5).…”

Does ICSI for in vitro fertilization cause more aneuploid embryos?

“…Preimplantation genetic testing for aneuploidies (PGT-A) has been widely applied in human in vitro fertilization (IVF), and has been one of embryo selection approaches apart from embryo morphology and timelapse culture with morphokinetic embryo selection [1][2][3][4][5][6][7]. However, high proportion of human embryos produced by IVF is aneuploidy that cannot be revealed by morphological assessment and morphokinetic embryo selection, thus PGT-A is considered as a valuable procedure to screen embryos' genetic status [1][2][3][4][5]. With PGT-A procedure, euploid embryos can be selected to transfer, which eventually can increase embryo implantation and reduce repeated implantation failures and birth defects [8][9][10].…”

Commentary re: Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

“…Given the increasing transition to NGS for diagnosis, it seems timely to review the baseline on which we have been operating prior to NGS. A good illustration of this is provided by Ravichandran et al, (2016) in this issue of RBM Online in an article concerning sex chromosome misdiagnoses at Reprogenetics between 2006 and 2013. The paper reports on 18,565 cycles subjected to cleavage stage (blastomere) biopsy and 2791 subjected to blastocyst (trophectoderm) biopsy.…”