18 January 2016
ByAppeared in BioNews 835
A new blood test for Down's syndrome in high-risk women has been recommended for use on the NHS.
The National Screening Committee said evidence shows that the new method, known as non-invasive prenatal testing (NIPT), is highly accurate and should reduce the number of pregnant women needing to undergo invasive amniocentesis.
'The NIPT test offers expectant mothers greater accuracy in screening for Down's Syndrome, with the use of a simple blood test,' Professor Lyn Chitty, from the UCL Institute of Child Health and Great Ormond Street Hospital and lead researcher on an evaluation study of the test, told the Telegraph.
'Introducing NIPT into NHS maternity care means that more women can be safely reassured about the health of their baby without having an invasive test, which increases the risk of miscarriage.
The test works by looking for DNA that has shed from the placenta and circulates in the mother's blood to identify chromosomal abnormalities, including those that cause Down's syndrome. It can also detect two other serious chromosome disorders, known as Edwards' and Patau's syndromes, in which babies usually die before or shortly after birth.
In the UK, all pregnant women are offered a combined blood test and ultrasound between 10-14 weeks to assess the risk of abnormalities. Women are considered high-risk on the basis of this test are offered an amniocentesis, in which a needle is inserted to take a sample of the amniotic fluid surrounding the fetus in the womb. This test is associated with a one percent risk of miscarriage and a small risk of serious infection.
The NIPT test, which could replace the amniocentesis test at this stage, is based on a simple blood sample from the mother. The fetal DNA in the sample is checked for chromosomal abnormalities in the laboratory – a process that takes around five days. Women who test positive may still undergo amniocentesis to receive a definitive diagnosis.
A study conducted at Great Ormond Street Hospital last year found that the NIPT test is 99 percent accurate and that more parents were willing to take this test than undergo amniocentesis (see BioNews 805).
Ministers still have to approve the recommendations before the test can be rolled out across the NHS.
Director of screening at Public Health England, Dr Anne Mackie, was positive about the new test, but said that important questions still remain. 'We don't know how good the test is for other genetic conditions – Edwards' and Patau's syndromes – that are currently part of the programme, and the evidence review also found that up to 13 percent of the NIPTs carried out didn't give any result at all,' she told the Guardian.
'The intention, therefore, is to monitor and evaluate as we go. That means rolling out the test across England in such a way that allows us to learn from the experience and alter the screening programme if necessary in light of any real-life findings.'