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ESHG Calls Use of Polygenic Risk Scores in Preimplantation Testing Unethical

NEW YORK – The claim that polygenic risk scores (PRSs) can predict an embryo's future health risks remains unproven, and their use in preimplantation testing is unethical, the European Society of Human Genetics said on Tuesday.

Members of ESHG's executive committee and public and professional policy committee, recently published a paper in the European Journal of Human Genetics, in which they assessed the current science underlying preimplantation genetic testing using PRS (PGT-P). There is no clinical research evaluating the diagnostic effectiveness of PGT-P, they wrote, and the procedure's utility remains "severely limited."

Nonetheless, some private testing companies already market PGT-P tests to parents seeking or considering in vitro fertilization.

Although genetic testing is standard in IVF, tests typically scan for disorders such as Down syndrome or cystic fibrosis, as these conditions are based on chromosomal abnormalities or monogenic, making the predictive power of such tests high.

"PRSs are a completely different matter," Francesca Forzano, chair of the ESHG public and professional policy committee, said in a statement. "Many conditions are caused by a combination of genetics and environment, and PRSs are only able to capture parts of any of the relevant genetic component, which is itself likely to be highly complex and difficult to analyze. In addition, while PRS may identify individuals at risk of a given disease in the general population (where the genetic variability is very wide), there is no evidence that they can be useful for a couple in determining the choice of one embryo over another, as the genetic variability within an individual family is limited."

Most current research involving PRS has been done on adults, with the aim of shedding light on the molecular mechanisms underlying complex diseases such as breast cancer. Data on pre-symptomatic PRS associations with long-term health outcomes is unavailable for embryos, and acquiring it would involve decadeslong studies, according to ESHG, as researchers would need to wait for predicted disorders to appear or not over the course of an individual's life.

Adding to these concerns, genome-wide association studies — from which PRS are derived — remain overwhelmingly biased toward people of European descent, meaning that data extrapolated from them may be of limited use to other populations.

The ESHG group determined that given the current knowledge gaps concerning the contribution of PRS to future health risks makes their use in preimplantation genetic testing "dangerously incomplete" and capable of causing "grave misunderstandings."

"At present," the group wrote, "carrying out a PRS test for embryo selection would be premature at best."

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