Preimplantation genetic testing for aneuploidy: A review of published blastocyst reanalysis concordance data

Abstract

Preimplantation genetic testing for aneuploidy (PGT-A) reduces miscarriage risk, increases the success of IVF, shortens time to pregnancy, and reduces multiple gestation rates without compromising outcomes. The progression of PGT-A has included common application of next-generation sequencing (NGS) from single nucleotide polymorphism microarray, quantitative real-time PCR, and array comparative hybridization platforms of analysis. Additional putative advances in PGT-A capability include classifying embryos as mosaic and predicting the presence of segmental imbalance. A critical component in the process of technical validation of these advancements involves evaluation of concordance between reanalysis results and initial testing results. While many independent studies have investigated the concordance of results obtained from the remaining embryo with the original PGT-A diagnosis, compilation and systematic analysis of published data has not been performed. Here, we review results from 26 primary research articles describing concordance in 1271 human blastocysts from 2260 pairwise comparisons. Results illustrate significantly higher discordance from PGT-A methods which utilize NGS and include prediction of mosaicism or segmental imbalance. These results suggest caution when considering new iterations PGT-A.

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

“…While intermediate copy number can indeed be caused by mosaicism, other factors such as assay noise/artifact, amplification bias, contamination, mitotic state, variation in embryo biopsy technique, embryology laboratory conditions, and laboratory thresholds set for calling mosaicism can all impact the assessed copy number 25,26,37 . Marin et al 26 . performed a meta‐analysis of blastocyst reanalysis and found that the concordance with the original mosaic result was only 42.6%.…”

“…14 By the blastocyst stage, an estimated 2% to 50% of embryo biopsies are reported to be mosaic, [15][16][17][18][19][20][21][22][23] with the wide range reflecting a combination of biological mechanisms (true mosaicism) 24 together with technological artifacts that stem from differences in assessing mosaicism from a single trophectoderm biopsy of three to seven cells. 25,26 Dissociation of blastocyst embryos show concordance of inner cell mass and trophectoderm biopsies in 95%-98% of embryos, 17,[27][28][29][30] suggesting that by the blastocyst stage, highlevel mosaicism confined to one of these two respective lineages is relatively rare (2%-5%; Figure 1a).…”

The origins of aneuploidy research consortium

“…Marin et al. report that the rates of discordancy between first and second analyses are partly attributable to technical considerations; rates were higher for programs using next generation sequencing methods for embryo analysis versus other technologies, and also higher for those programs that provide a prediction of mosaicism or segmental aneuploidy 27 …”

“…Marin et al report that the rates of discordancy between first and second analyses are partly attributable to technical considerations; rates were higher for programs using next generation sequencing methods for embryo analysis versus other technologies, and also higher for those programs that provide a prediction of mosaicism or segmental aneuploidy. 27 Benn and Grati show that the spectrum of aneuploidies present in first trimester chorionic villi are dependent on whether cytotrophoblast, mesenchyme, or both lineages are involved. 28 They also show that the number of genes in an imbalance is more important than physical size in determining the viability of pregnancies with imbalances.…”

The “mosaic” embryo: misconceptions and misinterpretations in preimplantation genetic testing for aneuploidy

“…This method is obviously incompatible with diagnosing mosaicism on a transferable embryo, but it provides superior evidence of bona fide mosaicism. A systematic review of studies that performed rebiopsies of embryos deemed mosaic on the basis of intermediate copy numbers revealed that most of those embryos (57%) were unlikely to have been mosaic (8). In addition, many embryos with chromosome copy numbers in the intermediate ''mosaic range" have been found to have a meiotic origin of aneuploidy consistent with uniform aneuploidy, further confirming the inaccuracy of predicting mosaicism by these methods (9).…”