(cffDNA) testing / Non -Invasive Prenatal Testing (NIPT) for Down's syndrome, Edwards' syndrome, Patau's syndrome
Last reviewed 01/2018
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:
- phescreening.blog.gov.uk @PHE_Screening (January 2016)
- NSC (June 2015). Frequently asked questions – cell free fetal DNA (cffDNA) testing for Down's syndrome and other trisomie