Experts have warned against the “unproven” and “unethical” use of genetic tests to predict the risk of complex diseases in embryos created through IVF.
Though not currently available in the UK, such tests are being marketed in the US and their availability is likely to increase as the technology develops, representatives from the European Society of Human Genetics (ESHG) said.
Writing in the European Journal of Human Genetics, they stressed that there is currently no evidence that the technique called polygenic risk score (PRS) analysis can predict the likelihood of as yet unborn children being at risk of complex diseases such as schizophrenia, type 2 diabetes or breast cancer in later life.
The geneticists also called for a societal debate about the future application of such tests, such as selecting for traits like height or intelligence.
“We believe that this is a highly promising field in genetics and for the prevention of disease, but at the [present] stage, it cannot be used,” said the ESHG president, Maurizio Genuardi, a professor of medical genetics at the Catholic University of the Sacred Heart in Rome. “There is no evidence that this kind of selection can lead to better or healthier babies.”
Unlike genetic testing for Down’s syndrome or diseases such as cystic fibrosis that are caused by mutations in a single gene, PRS aims to calculate an individual’s susceptibility to complex traits or disorders by combining the effects of dozens or potentially millions of genetic variants into a single figure. It involves analysing cells from embryos created through IVF, before they are implanted.
“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 analyse,” said Dr Francesca Forzano, the chair of the ESHG public and professional policy committee and a consultant in clinical genetics at Guy’s and St Thomas’ NHS foundation trust in London.
Even so, private testing companies are increasingly marketing such tests to prospective parents as a means of selecting embryos with a lower risk of disease in later life. At least one child has been born after such a procedure, Forzano and colleagues said.
Although US companies are leading the charge, “we do not really have a very good sense of what is happening in each individual private clinic across Europe and other countries,” said Forzano.
Sarah Norcross, the director of the Progress Educational Trust (PET), a charity that improves choices for people affected by infertility and genetic conditions, called on the Human Fertilisation and Embryology Authority to clarify the legal and regulatory status of such tests within the UK, and said the Advertising Standards Authority and Competition and Markets Authority should keep a careful eye on whether and how such tests are marketed to UK patients.
“PET supports this clear and unequivocal warning to fertility patients not to waste their money on having embryos tested using polygenic risk scores,” she said. “Even if – for the sake of argument, and despite a complete lack of clinical evidence – a polygenic risk score could meaningfully predict certain things about certain embryos, the sheer number of embryos that would be needed to make use of this test could not be achieved in a clinical setting.
“There are precious few embryos to choose from in a fertility treatment context, and so reasons for preferring one embryo over another must be grounded in clear evidence.”
The ESHG also called for a societal debate about the future application of PRS, to avoid discrimination and the stigmatisation of certain conditions. “If, theoretically, we are going to offer a test to select common traits, for which traits would our society consider it is ethical to offer?” said Forzano. “We need to consider whether we think that this is acceptable, whether it is ethical, and whether our society really wants to have something like that.”
by Linda Geddes