SNP microarray-based 24 chromosome aneuploidy screening is significantly more consistent than FISH

Abstract

Many studies estimate that chromosomal mosaicism within the cleavage-stage human embryo is high. However, comparison of two unique methods of aneuploidy screening of blastomeres within the same embryo has not been conducted and may indicate whether mosaicism has been overestimated due to technical inconsistency rather than the biological phenomena. The present study investigates the prevalence of chromosomal abnormality and mosaicism found with two different single cell aneuploidy screening techniques. Thirteen arrested cleavage-stage embryos were studied. Each was biopsied into individual cells (n = 160). The cells from each embryo were randomized into two groups. Those destined for FISH-based aneuploidy screening (n = 75) were fixed, one cell per slide. Cells for SNP microarray-based aneuploidy screening (n = 85) were put into individual tubes. Microarray was significantly more reliable (96%) than FISH (83%) for providing an interpretable result (P = 0.004). Markedly different results were obtained when comparing microarray and FISH results from individual embryos. Mosaicism was significantly less commonly observed by microarray (31%) than by FISH (100%) (P = 0.0005). Although FISH evaluated fewer chromosomes per cell and fewer cells per embryo, FISH still displayed significantly more unique genetic diagnoses per embryo (3.2 ± 0.2) than microarray (1.3 ± 0.2) (P < 0.0001). This is the first prospective, randomized, blinded and paired comparison between microarray and FISH-based aneuploidy screening. SNP microarray-based 24 chromosome aneuploidy screening provides more complete and consistent results than FISH. These results also suggest that FISH technology may overestimate the contribution of mitotic error to the origin of aneuploidy at the cleavage stage of human embryogenesis.

Preimplantation Genetic Screening (PGS) with Comparative Genomic Hybridization (CGH) following day 3 single cell blastomere biopsy markedly improves IVF outcomes while lowering multiple pregnancies and miscarriages

“…Studies comparing FISH with SNP array showed up to a 60 % false-positive rate with FISH. When FISH was compared to CCS, it was found that mosaicism was three times more common in FISH [35]. When compared to polar body biopsy it was found that blastomere biopsy with CCS was very accurate (94.2 %) when compared to trophoectoderm biopsy with CCS [3].…”

False positive rate of an arrayCGH platform for single-cell preimplantation genetic screening and subsequent clinical application on day-3

“…Further, embryo mosaicism at cleavage stage and self-correction of aneuploidies between cleavage stage and blastocyst stage have been noted [6]. Recent studies, however, suggest that both phenomena may be overestimated by day-3 FISH analysis [23,29]. To avoid any kind of misdiagnosis due to embryo mosaicism, polar bodies biopsies have been used [27], but in those cases, only maternal genetic information is obtained, thus all the paternal contribution as well as the mitotic errors are missed.…”

SNP array-based copy number and genotype analyses for preimplantation genetic diagnosis of human unbalanced translocations

“…33 On the basis of the above, we anticipate that further sample optimisation will increase PGD efficiency with respect to the detection of chromosomal imbalances and hence, the number of embryos suitable for transfer, in comparison with FISH studies. [36][37][38][39] There is some concern that SNP genotyping might detect predispositions to common and/or late-onset diseases. 20 However, we do not think that today's SNP resolution is high enough, as only blocks of informative SNP loci can be reliably used for haplo-or genotype analysis.…”