New test for genetic mutations to be offered to parents

A GENETIC test for prospective parents that could almost eliminate their chances of having children with inherited diseases such as cystic fibrosis has been developed by scientists.

The experimental technique, which identifies whether people carry genetic mutations that could cause up to 600 life-threatening disorders in their children, could be offered to British couples in trials as early as this summer, The Times has learnt.

The 400-pound procedure, whose cost is expected to fall to about pounds 130 within two years, raises the prospect of mass screening of young people before they become parents to prevent the birth of children with conditions such as sickle-cell anaemia.

Couples who learn that they are at risk of having an affected child could conceive by IVF and have the embryos screened so that only those without the disease are implanted into the womb.

Our goal is to eradicate all catastrophic recessive childhood diseases,” said Stephen Kingsmore, of Children’s Mercy Hospital in Kansas City, Missouri, who led the research.

The test covers more than four times as many disease genes as a similar procedure introduced last year by a company called Counsyl, and is also capable of identifying any mutation within them.

Both techniques are controversial because some doctors consider the diseases that they detect are too rare to justify screening people without a family history. They are also likely to increase demand for embryo screening, which some religious groups oppose, and to place extra pressure on GPs and genetic counsellors who would have to interpret the results.

Dr Kingsmore said that further research would be needed to confirm that the test was accurate in clinical settings before it became widely available, and he accepted that social issues would first need to be addressed.

“The social issues are very interesting and it is likely that different areas and groups will have different views about such testing and whether it should be normative or selective and at what age it should be offered and in what environment [community based or hospital based],” he said.

“Obviously there is a very strong need to ensure that this test is used pre-pregnancy rather than during pregnancy. There is a very strong need to ensure that appropriate counselling about family alternatives is available.”

The test, which is described in the journal Science Translational Medicine, detects genetic mutations that cause recessive diseases.

People who carry a single copy of these mutant genes are not ill themselves, but if a partner is also a carrier each of their children will have a one in four chance of inheriting two copies and developing the disease.

It can also pick up mutations carried by mothers on one of their two X chromosomes, which cause diseases such as haemophilia and Duchenne muscular dystrophy when inherited by their sons.

In the study, Dr Kingsmore’s team showed that the test can identify 448 genetic diseases with extremely high accuracy.

Since the paper was submitted, another 130 diseases have been added to create a panel of 580, and more are expected to follow.

The technique works by sequencing the DNA of more than 7,000 regions of the human genome, which include genes that malfunction to cause inherited disease.

Dr Kingsmore’s team is now refining how the test results are best interpreted, and will start evaluating it in clinics this year. One British centre is in discussions about taking part in trials.

Christine Patch, consultant genetic counsellor at Guy’s and St Thomas’ Hospital in London, said that screening everybody before parenthood may not be cost-effective. “As most people will carry some mutations, everybody is going to need genetic counselling, yet for most couples the risk will be very low.”

Alastair Kent, director of Genetic Alliance UK, a support network for families affected by inherited disease, said: “It is one thing to show that a test like this is scientifically accurate, but another to show that it can work in a clinical context.”

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