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Blood test for Down’s syndrome is safe and effective, say researchers

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h3126 (Published 08 June 2015) Cite this as: BMJ 2015;350:h3126
  1. Mathew Limb
  1. 1London

UK researchers are calling for non-invasive prenatal testing for Down’s syndrome to be introduced widely in the NHS on the basis of new study findings.

The results of an analysis carried out at Great Ormond Street Hospital for Children in London—whose laboratory is the first in the NHS to provide such testing—showed that it was safe, effective, and welcomed by parents, the researchers said.

Non-invasive testing checks maternal blood for fetal DNA indicative of Down’s syndrome and avoids the need for amniocentesis in most women.

Lyn Chitty, the lead researcher and professor of genetics and fetal medicine at Great Ormond Street, said that making the “more accurate” new test available on the NHS would reduce the amount of invasive testing, reduce numbers of miscarriages, and detect more cases of Down’s syndrome. “There’s huge inequality of access in the fact that the non-invasive prenatal test is available in the private sector and not in the NHS,” she told a media briefing in London on 5 June.

She said that big savings were possible, depending on the cost of the test itself and how it was implemented. Currently one in 200 women lose a baby after an amniocentesis, and this was “still a barrier to testing” for many women, said Chitty. “We are significantly reducing the risk of miscarriages, and it is very difficult to put a cost on that,” she said.

Preliminary findings from the unpublished study were due to be presented at the annual conference of the European Society of Human Genetics, being held in Glasgow on 6-9 June.

The study evaluated the possibility of introducing non-invasive prenatal testing into the NHS screening programme for trisomy 21 (Down’s syndrome). Currently all pregnant women in the United Kingdom are offered screening for Down’s syndrome, which is based on measurement of protein concentrations in the blood and nuchal translucency in the fetus. Any woman found to have a one in 150 or greater chance of having a fetus with Down’s syndrome is offered amniocentesis to make the diagnosis, and about 60% of these women opt for the procedure.

In the study, non-invasive prenatal testing was offered to women identified with a one in 1000 or greater chance of having a Down’s pregnancy. In the trial some 2500 women underwent the test, equivalent to 95% of those offered it.

Chitty said, “If we offered this test to all of the women who are currently offered an invasive test we would pick up more cases of Down’s than we do currently.

“At the moment only about 60% of women overall accept an invasive test if they’re told that they’re high risk, because they don’t want to put their baby at risk of miscarriage, whereas with NITP [non-invasive prenatal testing] 95% of them accept that and then NIPT will detect 99% of all cases of Down’s, so we’ll increase the detection.”

She said that the trial showed an 80% reduction in the number of invasive tests. Amniocentesis was still necessary to confirm diagnosis after a positive test result.

Chitty said an important finding was that around 30% of women who chose non-invasive testing “carried on” with their pregnancy rather than deciding to have an abortion. This showed that they wanted to be “forewarned of having a baby with Down’s rather than to elect to terminate the pregnancy,” she said.

The researchers will present their results later this month to the UK National Screening Committee.

Chitty said that the number of invasive tests for Down’s syndrome was already falling because non-invasive prenatal testing was available privately in the UK and abroad and that it would fall still further if non-invasive testing were available on the NHS.

Last September Chitty found that most women in the UK welcomed the opportunity to have a non-invasive test if they were found to be at high risk of carrying a fetus with Down’s syndrome.1

Notes

Cite this as: BMJ 2015;350:h3126

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