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Testing, Testing 1, 2, 3: PGS and PGD

26 September 2016
Appeared in BioNews 870

There was a captivating debate around the emerging genetic choices, legal framework and ethical issues from the use of PGS (pre-implantation genetic screening) and PGD (pre-implantation genetic diagnosis) at this event produced by the Progress Educational Trust (PET).

The event's chair Dr Sue Avery, who is a trustee of PET and director of the Birmingham Women's Fertility Centre, started off the discussion by asking whether experts and the general public can fully understand the current Human Fertilisation and Embryology Authority (HFEA) guidance on PGS and PGD.

The first speaker to take the stand was Dr Tony Gordon, who is managing director of Genesis Genetics in the USA and laboratory director of Genesis Genetics in the UK, the most experienced PGS and PGD laboratory. Dr Gordon explained that they perform tests for fertility clinics and are therefore distant from the patient and the HFEA.

Because his role has been divided between Europe and the USA, Dr Gordon has seen various PGS/PGD licensing systems, ranging from complete absence of regulation to the organised system of the UK. The HFEA has licensed more than 250 genetic tests that correspond to known genetic disorders, which are listed on their website by name and a bioinformatics number. The downside of this system is that it can take up to six months to gain a licence to test for a new genetic condition.

Dr Gordon said that karyomapping – a new, UK-invented technology – is often used nowadays for PGD. Next-generation sequencing is used for PGS. He explained that karyomapping looks at haplotypes rather than mutations, and that next-generation sequencing in this context is not whole-genome sequencing but is simply for counting chromosomes to identify aneuploidy.

The second speaker was Dr Christine Patch, a trustee at PET and clinical lead in genetic counselling at Genomics England. Dr Patch explained the purpose, intention and limitations of PGD and PGS. She explained that PGD is a technology that detects a particular genetic abnormality and therefore offers a reproductive choice to a couple with increased risk of passing on a genetic condition. PGS, by contrast, is performed to detect particular genetic variations which can decrease chances of implantation if present.

Dr Patch also discussed the costs involved in embryo testing – not just the financial costs but also the emotional costs, such as the cost of failed expectations or the cost of uncertainty. The patients may not know how to interpret the results nor understand how they are communicated back to them. These are important aspects of embryo testing.

We all have genetic variations, Dr Patch concluded, and patients are seeking the best chance to have a healthy baby.

The next speaker was James Lawford Davies, who is a partner at the law firm Hempsons. He gave a historical perspective on how the regulatory and legal framework for PGS and PGD was developed in the UK. He used examples of legal cases involving HFEA and three families, the Hashmis, the Whitakers and the Fletchers. Each of these families had requested tissue typing to produce a sibling and tissue donor for their first child, who was affected with an inheritable disease.

The legal outcomes for these families informed the Human Fertilisation and Embryology Act in 2008, which included provision for a number of scenarios requiring PGS, PGD and tissue typing.

With the technology advancing fast, Lawford Davies explained that in 2015 the HFEA requested legal advice for the use of PGD and PGS at the same time, as well as the use of PGD for more than one condition. The advice given to them stated that PGD and PGS should be considered separately and requirements for each should be satisfied. Consequently PGS is not a gateway to PGD and vice versa; patients must be eligible for both technologies if both are to be used.

As for the use of PGD for more than one condition, the HFEA was advised that it is possible to test for additional conditions, providing there is a satisfactory, 'significant' risk. Although these provisions are listed in HFEA's guidance, Lawford Davies raised concerns that they lack clarity, and so interpretations may vary.

The final speaker was Professor Michael Parker, who is professor of bioethics at the University of Oxford and director of the university's Ethox Centre. Professor Parker's take on the subject was based on his interest in genetic information and the additional information that can be produced by PGS and PGD. His main concern was how or under what conditions this knowledge should become available.

Professor Parker talked about patient-centredness and the current worry that health professionals may take decisions without proper acknowledgement of people's values. With the explosion of genetic research, he said, we tend to consider that people should not have access to choices unless their uncertainty can be managed or unless they fully understand the information given to them.

But then Professor Parker spoke about autonomy and social justice. He said that assurances should be put in place so that patients can make their own choices even in this context of uncertainty and open-endedness. He also talked about resources, including the availability of time, trained professionals and costs for making genomic information accessible. He wondered whether there will be a 'slippery slope' towards the selection of patients for these technologies. In principle, he said, if these services are cost effective, they ought to be available, and women should have access to this kind of information.

Next, it was over to the audience for their questions and comments. The themes raised by the audience included sex selection, the prospect of genome editing, the extent to which we understand genetic information today and how it should be handled, the broadness of the legal framework in the UK, and the increasingly complex issue of consent. The need to train more genetic counsellors was widely recognised by both the audience and the panel.

The panellists covered all concerns and reflected their final thoughts on the subject. They said that they are comfortable and pleased with how far PGS and PGD have come. Of course, there are ethical considerations, but work and progress seem harmonised within a legal framework that has been built well for the future.

Overall, it was a very stimulating and appropriately illuminating event for the hottest day in September.

PET is especially grateful to the event's sponsors, Illumina.

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5 July 2018 - by Shaoni Bhattacharya 
DNA shed from early embryos could one day provide an alternative way of genetically testing them without having to do a biopsy, suggests a small pilot study...
2 July 2018 - by Shaoni Bhattacharya 
Scientists say they have developed the most robust model yet to estimate how likely a woman is to have a chromosomally normal embryo for IVF depending on her age...
11 December 2017 - by Norbert Gleicher 
A seemingly brilliant hypothesis of preimplantation genetic screening arose in the 1990s when Dr Yuri Verlinsky proposed using polar body biopsies to detect chromosomal abnormalities in embryos prior to transfer in IVF... Healthy embryos are discarded by unvalidated PGS
6 March 2017 - by Matthew Thomas 
Dr Kat Arney leads a fascinating and wide-ranging discussion of genetic testing – from testing for cancer genes to whether your child's DNA can predict their future sporting ability...
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