UK approves preimplantation genetic screening technique
Annabel Ferriman, BMJ
British Medical Journal 2001;323:125 ( 21 July ) News

The screening of embryos for an abnormal number of chromosomes has been approved in principle by the Human Fertilisation and Embryology Authority, the body that regulates in vitro  fertilisation treatment in the United Kingdom.

It is the first time that the authority has approved a technique that detects a range of genetic abnormalities rather than one specific genetic disease. The technique, known as aneuploidy screening, is thought to increase the success rate of in vitro fertilisation by eliminating those embryos that have a poor chance of implanting in the womb.

In a statement issued last week, the authority said that while it recognised the potential of the technique, it would allow treatment only  within a strict framework of monitoring and control.

It was accused by Human Genetics Alert, a group that monitors developments in genetic medicine, of between testing individuals for specific genetic disabilities and a broad screening programme."

Because an abnormal number of chromosomes sometimes results in a child being born with Down's syndrome or another disorder, the group said that  the technique was a way of introducing a screening programme for Down's syndrome and other disabilities "by stealth."

The authority justified its decision by saying: "An embryo that is aneuploid contains an abnormal number of chromosomes and usually results  in a failure to implant or may miscarry. Screening for aneuploidy can benefit in particular those women who have suffered repeated miscarriage or IVF failure by identifying embryos that are mostly likely to successfully implant."

The authority issued the statement after one of its licensing committees  spent last Friday considering applications to introduce the procedure from the Assisted Reproduction and Gynaecology Unit in London, and the Centre for Assisted  Reproduction at the Park Hospital in Nottingham.

The authority said that it was "minded to issue licences," but that any such licence would be subject to an inspection of the intended laboratories, approval of clinic staff, provision of detailed technical and patient information, and ongoing monitoring.

Doubts about the introduction of aneuploidy screening were expressed this week not only by Human Genetics Alert, but by an expert in preimplantation genetic diagnosis and screening at Guy's and St Thomas's Hospitals NHS Trust, London.

Dr Paul Scriven, principal scientist at the trust, said: "The published data so far from the United States and Italy are still limited. It is not disputed that preimplantation genetic screening can increase the implantation rate per embryo transferred, but a significant increase in the clinical pregnancy rate per cycle started has yet to be demonstrated.

"An important factor is that significantly fewer embryos are likely to meet transfer criteria, due in part to the relatively low specificity of  the test," he explained. Dr Scriven said that it was too easy with present testing methods to misdiagnose a normal embryo as abnormal and therefore not attempt to transfer it into the womb.