British Society for Human Genetics press release
New technology has allowed the development of safer prenatal diagnosis by taking a maternal blood sample to analyse the cell free fetal DNA (cffDNA) which we now know circulates in the mother’s blood. Scientists say that as well as developing the laboratory techniques required to deliver this non-invasive prenatal diagnosis (NIPD), information for parents and health professionals is required along with a detailed health economic analysis.
This news comes as Professor Lyn Chitty, principal investigator, at UCL Institute of Child Health reports some of the early findings of the RAPID (Reliable, Accurate Prenatal non-Invasive Diagnosis) programme. This programme, launched in 2009, is funded by a £2 million Programme Grant from the National Institute for Health Research (NIHR) and aims to develop standards required to implement NIPD in the UK.
NIPD carries no risk to the pregnancy, unlike invasive methods (such as chorionic villus sampling and amniocentesis) which have around a 1% risk of miscarriage. It has been used successfully for fetal sex determination for women at risk of sex-linked disorders since 2003, but recent developments have seen research focus on single gene diseases, like sickle cell anaemia (SSA).
SSA is a blood disease caused by a single mutation – an affected fetus would have two copies of the error, while an unaffected fetus would have no copies, and a carrier one copy.
The cell free DNA present in the mother’s blood, which includes DNA from the mother and baby, is extracted, and sensitive counting methods are used to compare the number of copies of the mutation with the number of copies of the normal gene.
"We accurately identified the genetic status in all male fetuses, when the proportion of fetal DNA present was greater than 7%," said Professor Lyn Chitty, the RAPID Programme's principal investigator. "For females it's been more difficult, but by looking at a panel of markers inherited just from Dad we can see how much fetal DNA is present and have correctly identified the genetic status of the five female fetuses we have tested so far."
The researchers also explored the views of parents and health professionals on NIPD, and while both groups welcome these advances there are concerns that, as the procedure only involves a simple blood test, parents may not fully consider the possible implications.
In a survey of practitioner opinions, one genetic counsellor commented: “With a non-invasive test people might have it more readily without thinking through whether they want that information.”
The RAPID programme is working with health professionals and patient groups to create information and training packages that will help the transition of these tests from laboratory to clinic in the future.
“NIPD for Down’s syndrome is the next major hurdle,” explained Professor Chitty. “There have been big advances in this area but there is much that needs to be done before it will be available in the UK. In addition to developing the laboratory and pre-test counselling standards, the National Screening Committee will need to look at implementation as it may result in significant changes to service delivery.”
Professor Lyn Chitty's comments come in advance of a talk she will give about her work at 11.15am on 7th September 2011 at the annual BSHG conference held at the University of Warwick from 5th to 7th September 2011.
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