Friday, January 14, 2011

Simple blood test may predict Down syndrome

From New Scientist:

A simple blood test for Down's syndrome could provide an alternative to invasive testing in pregnant women.

Over 700 women from Hong Kong, the UK and the Netherlands at risk of having a fetus with Down's underwent the new screening procedure. Researchers successfully detected Down's in all 86 confirmed cases. The researchers believe 98 per cent of invasive diagnostic procedures could be avoided.

Speaking to the BBC, Kypros Nicolaides of King's College London, who worked on the study, said: "Women, understandably, are fearful of invasive tests. This extra screen is non-invasive and would save many from needing further investigation."

Our understanding and treatment of Down's syndrome has certainly improved since it was first identified in 1866. We know the condition is caused by an extra copy of chromosome 21, that the risk factor for having a child with the condition increases with maternal age and that people with the extra chromosome display impaired cognitive ability and altered physical characteristics.

Until now however, screening for Down's has been invasive. Samples of genetic material from the fetus are typically obtained by amniocentesis, whereby a sample of amniotic fluid that surrounds the fetus is removed by a needle, or chorionic villus sampling in which a sample of the placenta is removed.

These tests carry around a one per cent risk of miscarriage and may lead to fetal injury. Although Down's itself cannot be treated, many of its complications are preventable or treatable. These new non-invasive screening techniques could encourage women to take them who might otherwise be put off by the risks associated with current testing procedures, particularly if the chances of miscarriage are greater (one in 100) than the chances of having a child with Down's (one in 110 for a 40-year-old woman).

Previously, Lyn Chitty, who studies fetal medicine at University College London, had deemed studies using blood tests by the same researchers as "not ready for use in the UK". Speaking on the BBC's Today programme, Nicolaides says they now have a technique that "is feasible to use in clinical practice".