New non-invasive test could detect Down's syndrome during pregnancy, experts say

The procedure could prevent hundreds of women having invasive tests

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Indy Lifestyle Online

More cases of Down’s syndrome could be detected during pregnancy, and hundreds of women could avoid invasive tests, if the NHS were to introduce a new DNA blood test for the condition, experts have said.

Trials of non-invasive prenatal testing (NIPT), which only requires a blood sample from the mother, at eight hospitals in England and Scotland, found that women were more willing to take the test and that it could detect Down’s syndrome with 99 per accuracy.

Currently, all pregnant women are offered ultrasound and blood tests to screen for Down’s syndrome and other conditions. Those found to have a risk greater than 1 in 150 must decide whether to have a further test, which involves a needle being inserted into the womb, and also carries a 1 in 100 risk of miscarriage.

Because of the risks only 60 per cent of women take up this test.

However, in the trials, involving more than 2,500 women, mothers were offered either NIPT or the invasive test and 95 per cent opted to take a test – the vast majority choosing NIPT.

Women who received a positive NIPT test still needed to have the invasive test to confirm a Down’s syndrome diagnosis, but overall the number of women having an invasive test was 85 per cent lower than in the general population.

Professor Lyn Chitty of University College London and Great Ormond Street Hospital, who led the trials, said that the new test had the potential to be rolled out throughout the NHS, and would be likely to improve detection, and reduce the number of miscarriages.

It is already available privately, where it can cost between £400 and £900.

“There was a very high uptake of testing and we saw invasive test numbers fall sharply. NIPT performed well in identifying problems, and women were very positive about it,” she said.

Most women who receive an antenatal diagnosis of Down’s syndrome decide to terminate the pregnancy. In 2008, the proportion was 92 per cent of women.

Professor Chitty said that one of the concerns about NIPT was that detecting more cases might reduce the number of Down’s syndrome children being born, and thus could be said to discriminate against them. However, she said she expected the proportion of women who opted to continue their pregnancy after a positive diagnosis would be the same, regardless of testing method.  

The findings from the study, which will be reported at the conference of the European Society of Human Genetics, will be presented to the NHS’ screening authority, the UK National Screening Committee (UKNSC) later this month. The UKNSC said it would look at the results and other international evidence in order to make a recommendation on whether NIPT can be rolled out as part of the NHS screening programme.