Parental gene carrier testing could soon be available

A new genetic test could lead to the elimination of hundreds of inherited diseases, US scientists claim.

The test will allow prospective parents to learn of their risk of having a child with a recessive inherited disease before they conceive. Couples at risk may then opt for IVF with embryo screening to ensure that only embryos without the disease are implanted.

'Our goal is to eradicate all catastrophic recessive childhood diseases', said Dr Stephen Kingsmore, from Children's Mercy Hospital in Kansas City, who led the research.

Recessive diseases, such as cystic fibrosis and sickle-cell anaemia, occur when two copies of the disease gene are inherited together. A person with one copy will not develop the disease themselves, but when two people carrying a copy of the same mutation conceive, the chance of their offspring inheriting two copies and developing the disease is one in four.

Dr Kingsmore said: 'On average we found that each of us carries two or three mutations that could cause one of these severe childhood diseases. Of course, a person would have to be unlucky enough to be having a baby with someone who just happened to be carrying a mutation for the same rare disease'.

At present 448 recessive diseases are covered by the test, which involves sequencing over 7,000 regions of the genome to identify disease-causing mutations. This is significantly more than the scope of similar tests currently available and is set to increase to 580 in the coming months: 'At which point we'll have represented just about every childhood disease that's severe enough to merit inclusion', added Dr Kingsmore.

However, the development of such a test is not without controversy, with some claiming that recessive diseases are too rare to justify screening couples without a family history. The demand for embryo screening - a procedure opposed by many religious groups - is also likely to increase, and all couples who take the test will require genetic counselling, raising concerns over the cost-effectiveness.

'As most people will carry some mutations, everybody is going to need genetic counselling, yet for most couples the risk will be very low', said Dr Christine Patch, a consultant genetic counsellor at Guy's Hospital in London.

Dr Kingsbury and his team are now focusing on finding the best way to interpret the test results and hope to start trialing the test in clinics this summer, with one British centre set to take part.

However Alastair Kent, director of Genetic Alliance UK, urged caution, warning: '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'.