Genetic Testing 101
What must you know about preimplantation genetic testing when going through IVF and should you consider it? We talk with Rachael Cabey, a Licensed Certified Genetic Counselor and a lead laboratory genetic counselor for Cooper Genomics and Jenna Miller, a Licensed Certified Genetic Counselor and a clinical science liaison for Cooper Genomics. Jenna travels around the US educating clinicians about genomics and genomic testing.
Hit the Highlights
- Understanding the terms.
- Pre-2019
- Preimplantation Genetic Testing (PGT)
- Preimplantation Genetic Screening (PGS)
- Preimplantation Genetic Diagnosis (PGD).
- Current Terminology
- PGS is now Preimplantation Genetic Testing for Aneuploidies (PGT-A).
- PGD is now Preimplantation Genetic Testing for Monogenic/Single-Gene Disorders (PGT-M)
- Preimplantation Genetic Testing for Chromosomal Structural Rearrangements (PGT-SR)
- Pre-2019
- PGT-A
- What is PGT-A?
- Aneuploidy can cause what adverse outcomes?
- How many chromosomes can be screened for?
- Who should consider having this testing?
- What can PGT-A show us?
- Whole Chromosomal that are extra or missing.
- Difficult to detect a balanced translocation.
- What is a Polyploidy?
- Segmental aneuploidy? Smaller deletions or duplications
- Because the missing or extra piece of chromosome is less severe than a whole extra or missing chromosome, segmental aneuploidies have a higher chance or resulting in a child born with physical or intellectual disabilities.
- What do we mean by the resolution of the testing?
- Is it possible to determine from which parent (the egg or sperm) the chromosome abnormality originated? Why might this be important?
- What are the different testing platforms that can be used with PGT-A?
- Next Generation Sequencing (NGS)
- Single NucleotidePolymorphisms (SNPs)
- Mosaicism
- What is mosaicism? (the presence of a mixture of chromosomally normal and abnormal cells)
- Not related to maternal age. Occurs after fertilization.
- Are there different degrees of mosaicism?
- Does the presence of mosaicism impact the implantation rate, miscarriage rate, and birth defect rate?
- What does the research show on how PGT-A impacts the success rate of IVF?
- How is the test performed?
- How accurate is PGT-A testing? What is the risk of false negatives and false positives?
- Preimplantation Genetic Testing for Monogenic/Single-Gene Disorders (PGT-M)
- What is PGT-M? (looks for specific inherited conditions controlled by a single gene)
- Alternative options
- Who should consider having this testing?
- Does PGT-M impact the success rate of IVF?
- Does this testing process differ from PGT-A?
- How accurate is PGT-M testing?
- Preimplantation Genetic Testing for Chromosomal Structural Rearrangements (PGT-SR)
- What is PGT-SR?
- Who should consider having this testing?
- Does this testing process differ from PGT-A or PGT-M?
- How accurate is PGT-SR testing? Same range mid to high 90%
- Important Additional Information
- Patients and health care providers should be aware that a “normal” or negative preimplantation genetic test result is not a guarantee of a newborn without genetic abnormalities.
- Importance of genetic counseling.
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Music credit: Michael Ashworth
Photo credit: Gerd Altmann from Pixabay