Non-invasive Down's syndrome test 'ready for NHS'

Researchers say that a non-invasive prenatal test (NIPT) for Down's syndrome is ready to be introduced into the NHS.

The team, from Great Ormond Street Hospital in London, showed that the blood test could detect Down's syndrome in 99 percent of cases.

Furthermore, it could reduce the number of women who undergo amniocentesis during pregnancy, which carries a one in 200 risk of miscarriage.

'There was a very high uptake of testing and we saw invasive test numbers fall sharply,' said lead researcher Professor Lyn Chitty. 'NIPT performed well in identifying problems, and women were very positive about it.'

The researchers identified pregnant women with a one in 1000 risk of having a baby born with Down's syndrome and offered them NIPT. If the test was positive, they were then referred for confirmation by amniocentesis.

The researchers found that the test was highly accurate, with only five false-positive results, and it also had very high uptake - 95 percent compared with a typical uptake of around 60 percent under the current system.

It works by detecting fetal DNA that has shed from the placenta and circulates in the mother's blood. Blood samples were analysed using a technique called 'massively parallel sequencing' to look for an excess of genetic material from chromosome 21, which is duplicated in Down's syndrome.

The trial was carried out at eight UK maternity units, who were provided with training and educational materials. Overall, 2,500 women underwent NIPT from a population of around 40,000.

The researchers, who presented their findings at the European Society of Human Genetics conference in Glasgow, estimate that the test costs around £250 per mother.

'The cost of providing an NIPT service will depend on the cost of the test itself and how it is implemented. There will be significant savings resulting from a decrease in invasive testing whilst increasing the detection of affected babies,' Professor Chitty said.

She also notes that the test should consequently lead to fewer miscarriages and 'it's hard to put a price on that'.

The test - known as RAPID - is already available privately at Great Ormond Street Hospital. Later this month, the researchers will present their findings to the UK National Screening Committee, which will decide whether to roll it out across the NHS.