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(cffDNA) testing / Non -Invasive Prenatal Testing (NIPT) for Down's syndrome, Edwards' syndrome, Patau's syndrome

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UK NSC non-invasive prenatal testing (NIPT) recommendation

The UK NSC recommended an evaluative implementation of NIPT to assess what impact it would have on the existing NHS Fetal Anomaly Screening Programme

  • pregnant women are already offered a screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome from 10-14 weeks of pregnancy (the combined test, involving an ultrasound scan and blood test), or a screening test for Down's syndrome only (the quadruple test, involving a blood test alone) if booking between 14-20 weeks

  • if the screening test shows that the chance of having a baby with Down's, Edwards' and Patau's syndromes is higher than 1 in 150, this is called a higher-risk result. Currently, women who have a higher risk result have the option of having an invasive diagnostic test (amniocentesis or CVS)

  • the proposed change is for Non-Invasive Prenatal Testing to be offered to women who are deemed at higher risk following the current primary screen. NIPT is not diagnostic and an invasive diagnostic test is still required to receive a definitive diagnosis

Key findings supporting the UK NSC recommendation

  • an invasive diagnostic test carries a small risk of miscarriage. The evidence suggests that NIPT will reduce the number of women being offered an invasive test

  • however, while we know that the accuracy of NIPT is very good, we don't yet know how it will perform in an NHS screening programme pathway

  • for women who choose to have NIPT, this will add in an extra step in the screening programme. The impact of this, and the choices women make at different points in the pathway, is something that we hope to gain a better understanding of through further research

  • a recommendation has therefore been made to evaluate the introduction of non-invasive prenatal testing (NIPT) to Down's syndrome screening. This will include scientific, ethical and user input to better understand the impact on women, their partners and the screening programme around the offer of cfDNA or invasive testing following a screening test result where:
    • the screening test risk score for trisomy 21 (T21) is greater than or equal to 1 in 150
    • the combined test risk score for trisomy 18 (T18) and trisomy 13 (T13) is greater than or equal to 1 in 15

Notes (2):

  • cell free fetal DNA (cffDNA) testing , also known as Non -Invasive Prenatal Testing or NIPT, is a test that can identify pregnant women who are at higher risk of having a baby with certain genetic and chromosomal conditions , such as Down's syndrome (also known as Trisomy 21), Edwards' syndrome (Trisomy 18 ) and Patau's syndrome (Trisomy 13)

  • the test detects DNA fragments in a sample of blood taken from the mother. Most of the DNA fragments are from the mother but some are from the unborn baby, these fragments are called cell free fetal DNA (cffDNA) . CffDNA is detectable from around 7 weeks of pregnancy and the amount of detectable DNA is thought to rise as the pregnancy continues

Reference:

Last reviewed 01/2018

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