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New NHS screening for Down's expected soon

DNA test will improve performance in screening and reduce miscarriages

Mark Gould

Tuesday, 27 October 2015

Next week, UK screening experts are expected to recommend the introduction of a long-awaited DNA blood test which would improve performance in screening for Down's syndrome and cut the rate of miscarriages related to current more invasive tests.

At present, women who are between 11 and 14 weeks pregnant are offered a blood test and ultrasound scan, known as the combined test. A new study* of over 15,000 women in the journal Ultrasound in Obstetrics and Gynaecology found that the new DNA test more accurately identifies pregnancies with Down's syndrome. The new test is able to detect small fragments of DNA from the baby floating about in the mother’s blood, called cell-free DNA (cfDNA).

Currently, risk of carrying a baby with Down’s syndrome is based on age, hormone levels and a “nuchal scan” of fluid collection at the unborn baby’s neck. Women deemed to be high risk following this “combined assessment” are given the option of further tests, which involve chorionic villous sampling or amniocentesis. Both methods are still the only tests that can provide a definitive diagnosis of Down’s syndrome, but carry a risk of miscarriage.

The new study involved 11,692 women with single pregnancies treated at two different hospitals – King’s College Hospital in London and the Medway Maritime Hospital in Kent.

A small proportion of these women (395) were found to be at high-risk for Down’s syndrome. The results of the study suggested that the best approach to screening for Down’s syndrome was to offer the combined test to all pregnant women and, based on the results, to select a group that would benefit from the cell-free DNA test.

The study also found that the DNA test could be easily incorporated into routine clinical care within the NHS, and was the preferred option for pregnant women. In this way, the researchers said a higher proportion of affected pregnancies can be identified, resulting in a small increase in the overall cost to the NHS, but a major decrease in invasive tests.

Lead author Professor Kypros Nicolaides, from King’s College Hospital and King’s College London, who is the director of the Harris Birthright Research Centre for Foetal Medicine at King’s, said: “Our research puts the case for offering the cell-free DNA test on the NHS. This would improve the performance of screening, and reduce the number of unnecessary invasive tests and miscarriages."

A Public Health England spokesman said: "The UK NSC is currently consulting on introducing non-invasive prenatal testing (NIPT) to the existing foetal anomaly screening programme (FASP). A recommendation is expected to be made at the next UK NSC meeting in November."

* Nicolaides KH, et al. Clinical implementation of routine screening for fetal trisomies in the UK NHS: cell-free DNA test contingent on results from first-trimester combined test. Ultrasound in Obstetrics & Gynecology, October 2015. DOI: 10.1002/uog.15783

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