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Expanded Carrier Screening in Egg, Sperm Donors Raises New Issues, Genetic Counselors Find

SEATTLE (GenomeWeb) – Genetic counselors working in the area of assisted reproductive technologies are grappling with the most appropriate strategies for using sperm or egg donors' disease carrier information as the industry begins moving toward expanded carrier screening tests.

At the National Society of Genetic Counselors annual education conference here this week, speakers at a session on genetic screening and risk assessment for gamete donors addressed the importance of genetic test outcomes, family medical history, and psychiatric assessments of gamete donors in the context of current American Society for Reproductive Medicine (ASRM) guidelines for gamete donor screening.

Though expanded carrier screening is not the current standard of care, panelists urged genetic counselors to be aware of such issues and called for updates to the guidelines surrounding gamete donor eligibility to address the changing technology used to identify recessive disease carriers.

In particular, Lauri Black, a genetic counselor at the Pacific Fertility Center Egg Donor Agency and Frozen Egg Bank, described findings from a six-month study of potential egg donors who had expanded carrier screening with Natera's Horizon Screen, which considers carrier status for 254 autosomal recessive and 20 X-linked conditions. The would-be donors also underwent karyotyping and tests related to conditions such as Tay-Sachs disease.

Between February and August of this year, Black counseled 94 potential egg donors. All of them consented to have expanded carrier screening, she explained, in part due to curiosity about their own genetic data. Of those, 78 went through with the testing, while the remaining individuals dropped out or were disqualified from donation for other reasons.

The women also provided three-generation pedigree information to get a look at their family histories and went through a standard psychiatric evaluation.

As part of the expanded carrier screening consent process, the participants were apprized of the need to let family members know if they did have a positive result on the carrier screening panel, but were also assured it was very unlikely that a positive carrier test would impact their own health.

All told, Black and her colleagues identified 52 recessive disease carriers, representing roughly two-thirds of potential donor women who underwent testing. Most of those — around 63 percent — were carriers for one recessive condition, while others were carriers for as many as four recessive conditions.

Such results are not necessarily surprising, Black said, but raise important questions about the consequences of a positive carrier test — from the information that should be returned to the donors and intended parents to the appropriate level of risk, if any, to convey during counseling. 

Although recessive disease carriers are not excluded as egg donors, panelists at the session cautioned that egg donor carrier status should be carefully considered alongside genetic profiles from the intended father or sperm donor to ensure they do not share risk for a given recessive disease.

There are other gray areas as well. While ASRM guidelines are clear about disqualifying potential gamete donors who have known karyotypic abnormalities or major Mendelian disorders, other genetic features are more open to interpretation.

For example, gamete donors may theoretically be excluded if there is a disease with a major genetic component in their family — information that is not always available, even when counselors, clinics, gamete recruitment agencies, and physicians can agree on the diseases that fall into that category.

And in an industry where features such as male height or female appearance are often inordinately valued, panelists argued, risk for genetic conditions may not always be front of mind without input from genetic counselors or other professionals in the field.

There are also issues related to the timing of detailed genetic or related family history evaluations, Bay Area Genetic Counseling founder Amy Vance said, highlighting examples of potential donors she has worked with who later turned out to have family histories excluding them from donation.

Since many aspiring donors are never selected, some agencies do not want to shoulder the cost of genetically vetting them each in detail until a family has made their donor choice and perhaps even paid a deposit. In the quest to have a healthy baby, the intended parents may be faced with difficult decisions about whether to go forward with a given donor if possible genetic concerns do arise at that point, Vance said.