Survey on Mosaicism in Preimplantation Genetic Screening (PGS): what is your opinion?
It is now apparent that mosaicism exists in a material number of embryos as part of the human conception, and some PGS technolgies are now able to detect its presence. This survey is designed to evaluate the extent of mosaicism in PGS clinical practice and to gain insight on the views and practices of the ART community regarding this issue. Your opinion is important whether you perform PGS or not
Background
Aneuploidy is the leading cause of implantation failure, miscarriage and congenital abnormalities in humans. It is for this reason that preimplantation genetic screening (PGS) was introduced into clinical practice. By transferring only chromosomally normal embryos the clinical outcomes of artificial reproduction techniques (ART) could be potentially improved. Initially, PGS has been performed using fluorescence in situ hybridization (FISH) but its efficiency has been questioned in some studies. One reason why FISH was ineffective has been the fact that only a limited number of chromosomes could be analyzed.
Current PGS practice employs comprehensive chromosomal screening of all 24 chromosomes using either array comparative genomic hybridization (aCGH) or, more recently, next-generation sequencing (NGS) in multicellular biopsy samples from the trophectoderm of blastocysts. However, these techniques, particularly NGS, have unveiled the phenomenon of mosaicism - the presence of cell lineages with different chromosomal constitution. The medical and scientific communities are still uncertain how best to deal with this phenomenon. It is thus the purpose of this survey to evaluate the extent of mosaicism in PGS clinical practice and to gain insight on the views and practices of the ART community regarding this issue.
Is preimplantation genetic diagnosis for aneuploidy screening (PGS) currently being used in your clinic?
YES
What is the number of PGS cycles performed in your center per year?
- 10 cycles
- 10-50 cycles
- 50-100 cycles
- 100-200 cycles
- >200 cycles
At what stage of development are the majority embryos biopsied in your center?
- Polar body biopsy (PB1 and PB2)
- Polar body biopsy (PB1 only)
- Blastomere biopsy (1 cell)
- Blastomere biopsy (>1 cell)
- Trophectoderm biopsy (day 5 only)
- Trophectoderm biopsy (day 5 or 6 depending blastocyst stage)
In trophectoderm biopsy what is the optimal number of cells that you aim to obtain?
- Less than 5
- 5-7
- 8-10
- More than 10
Which method is predominantly used in your center for PGS?
- FISH
- Array CGH
- Real-time quantitative PCR
- SNP microarray
- Next generation sequencing
- Other
- I don't know
Where is genetic testing being performed in the majority of cases in your center?
- In-house genetic laboratory
- Centralized/referral laboratory
Do you receive information on mosaicism from the laboratory?
- Yes – any degree of mosaicism is reported as ‘mosaic’ for the chromosome(s) involved
- Yes – any degree of mosaicism is reported as ‘mosaic’ and the % mosaicism is provided for the chromosome(s) involved
- Yes – the sample is reported as ‘mosaic’ for the chromosome(s) involved but only above a certain mosaicism threshold
- Yes – the % mosaicism for the chromosome(s) involved is reported but only above a certain mosaicism threshold
- No – samples are reported as euploid or aneuploidy only
- Other
What is the percentage of mosaic embryos that you encounter in your practice?
- Less than 5%
- 6%-10%
- 11%-20%
- More than 20%
- I don’t know
Do you ever re-biopsy mosaic embryos?
- Yes
- No
- Only under special clinical circumstances
At what level of mosaicism would you do you consider the embryo as abnormal?
- More than 10%
- More than 20%
- More than 30%
- More than 40%
- More than 50%
- I don’t know
Should mosaic embryos be stored for potential therapeutic use or discarded?
- Should be stored for potential therapeutic use
- Should be discarded
- Should be stored for potential therapeutic use following individual counseling
Should mosaic embryos be transferred?
- Yes, if no euploid embryos are available for transfer
- No, mosaic embryos should never be transferred
- Yes, but only if mosaicism degree is below a certain threshold
- Yes, but it depends on the specific chromosome involved
What kind of mosaic embryos would you consider transferring?
- Only monosomic
- Both monosomic and trisomic
- All mosaic embryos below a certain threshold
- I would never consider transferring mosaic embryos
- It would depend upon the specific chromosome involved
How would you follow a pregnancy following transfer of mosaic embryos?
- Like any other IVF-PGS pregnancy
- Recommend invasive prenatal testing (CVS)
- Recommend invasive prenatal testing (amniocentesis)
- Recommend non-invasive prenatal testing (NIPT)
- Recommend genetic counseling
Do you think next generation sequencing is required to reliably detect mosaicism?
- Yes
- No
- I do not know
Which of the following statements best describes your views regarding mosaicism in preimplantation embryos?
- Mosaicism is a serious problem that puts in doubt the entire concept of PGS. Until the issue is resolved, the use of PGS should be avoided.
- Mosaicism is a problem but with proper counseling the practice of PGS should continue
- Mosaicism is not a problem and should not influence the practice of PGS.
- Mosaicism, while challenging, provides an opportunity to further discriminate between embryos during PGS
- Mosaicism may be an issue, but has always existed in IVF. More study is needed, but PGS should continue with appropriate safeguards and counseling.
- The concern over mosaicism in human embryos is exaggerated by over-sensitive technology
What types of studies would be most valuable to better understand mosaicism? (select all that apply)
- Better characterization of detection limits and technical requirements of PGS technologies for mosaicism detection
- Retrospective studies using NGS of samples previously tested with other PGS methods to establish the ’true’ incidence of embryo mosaicism
- Retrospective studies using NGS of embryos previously tested euploid with other methods to establish the clinical impact of mosaicism
- Prospective studies about the impact of mosaicism on clinical outcomes
- Distribution of mosaicism throughout embryos donated for research (e.g. multiple biopsies for each embryo) and between TE biopsy and ICM
- Other
Which of these is most critical in the short term?
- Better characterization of detection limits and technical requirements of PGS technologies for mosaicism detection
- Retrospective studies using NGS of samples previously tested with other PGS methods to establish incidence of embryo mosaicism
- Retrospective studies using NGS of embryos previously tested euploid with other methods to establish the clinical impact of mosaicism
- Prospective studies about the impact of mosaicism on clinical outcomes
- Consistency/distribution of mosaicism throughout embryos (e.g. multiple biopsies for each embryo) and between TE biopsy and ICM
- Other
NO
At what level of mosaicism would you do you consider the embryo as abnormal?
- More than 10%
- More than 20%
- More than 30%
- More than 40%
- More than 50%
- I don’t know
Should mosaic embryos be stored for potential therapeutic use or discarded?
- Should be stored for potential therapeutic use
- Should be discarded
- Should be stored for potential therapeutic use following individual counseling
Should mosaic embryos be transferred?
- Yes, if no euploid embryos are available for transfer
- No, mosaic embryos should never be transferred
- Yes, but only if mosaicism degree is below a certain threshold
- Yes, but it depends on the specific chromosome involved
What kind of mosaic embryos would you consider transferring?
- Only monosomic
- Both monosomic and trisomic
- All mosaic embryos below a certain threshold
- I would never consider transferring mosaic embryos
- It would depend upon the specific chromosome involved
How would you follow a pregnancy following transfer of mosaic embryos?
- Like any other IVF-PGS pregnancy
- Recommend invasive prenatal testing (CVS)
- Recommend invasive prenatal testing (amniocentesis)
- Recommend non-invasive prenatal testing (NIPT)
- Recommend genetic counseling
Do you think next generation sequencing is required to reliably detect mosaicism?
- Yes
- No
- I do not know
Which of the following statements best describes your views regarding mosaicism in preimplantation embryos?
- Mosaicism is a serious problem that puts in doubt the entire concept of PGS. Until the issue is resolved, the use of PGS should be avoided.
- Mosaicism is a problem but with proper counseling the practice of PGS should continue
- Mosaicism is not a problem and should not influence the practice of PGS.
- Mosaicism, while challenging, provides an opportunity to further discriminate between embryos during PGS
- Mosaicism may be an issue, but has always existed in IVF. More study is needed, but PGS should continue with appropriate safeguards and counseling.
- The concern over mosaicism in human embryos is exaggerated by over-sensitive technology
Do you think next generation sequencing is required to reliably detect mosaicism?
- Yes
- No
- I do not know
Which of the following statements best describes your views regarding mosaicism in preimplantation embryos?
- Mosaicism is a serious problem that puts in doubt the entire concept of PGS. Until the issue is resolved, the use of PGS should be avoided.
- Mosaicism is a problem but with proper counseling the practice of PGS should continue
- Mosaicism is not a problem and should not influence the practice of PGS.
- Mosaicism, while challenging, provides an opportunity to further discriminate between embryos during PGS
- Mosaicism may be an issue, but has always existed in IVF. More study is needed, but PGS should continue with appropriate safeguards and counseling.
- The concern over mosaicism in human embryos is exaggerated by over-sensitive technology
What types of studies would be most valuable to better understand mosaicism? (select all that apply)
- Better characterization of detection limits and technical requirements of PGS technologies for mosaicism detection
- Retrospective studies using NGS of samples previously tested with other PGS methods to establish the ’true’ incidence of embryo mosaicism
- Retrospective studies using NGS of embryos previously tested euploid with other methods to establish the clinical impact of mosaicism
- Prospective studies about the impact of mosaicism on clinical outcomes
- Distribution of mosaicism throughout embryos donated for research (e.g. multiple biopsies for each embryo) and between TE biopsy and ICM
- Other
Which of these is most critical in the short term?
- Better characterization of detection limits and technical requirements of PGS technologies for mosaicism detection
- Retrospective studies using NGS of samples previously tested with other PGS methods to establish incidence of embryo mosaicism
- Retrospective studies using NGS of embryos previously tested euploid with other methods to establish the clinical impact of mosaicism
- Prospective studies about the impact of mosaicism on clinical outcomes
- Consistency/distribution of mosaicism throughout embryos (e.g. multiple biopsies for each embryo) and between TE biopsy and ICM
- Other
