NIPT in summary:
- Better detection rates (more accurate)
- Less chance of a false positive result
Most likely your first scan on the NHS will be at 12 weeks as part of the screening programme for Down’s syndrome (sometimes referred to as the NT scan).
On the NHS, this screening test is called the ‘combined-screening’ test and consists of an ultrasound scan to measure Nuchal Translucency (NT), a packet of fluid at the back of the baby’s neck, combined with a blood test looking at pregnancy hormones using a sample of blood taken from the arm.
Taken together, these measurements mean that a computer programme can calculate a risk of your baby being affected with Down’s Syndrome and 2 other chromosomal conditions (Edwards and Patau’s syndrome).
However, for at least three reasons, NIPT is considered a better test than the combined screening test.
Accuracy: NIPT compared to the Combined-Screening Test
‘NIPT is more accurate than the combined or quadruple test for estimating the risk of Down’s syndrome’- NHS (rapid.nhs.uk)
NIPT (or Non-Invasive Prenatal Testing) is currently the simplest, most accurate and risk-free screening test you can have and from as early as 9 weeks’ in pregnancy. It still calculates the risk of the pregnancy being affected by a trisomy condition such as Down’s, Edwards’ or Patau’s Syndrome but it will detect 99.9% of Down’s affected pregnancies.
To compare, the combined screening test has a detection rate of 75 – 90% depending on the hospital you are screened in (ask your local screening coordinator for their current hospital figures).
The Non-invasive Screening is currently offered mainly privately within the UK with only a few NHS centres offering as research or to high-risk pregnancies only. It is currently not a standard screening test yet but the NHS is reviewing its implementation.
You can opt for NIPT screening with this is my: baby without the need for a referral from your GP, midwife or healthcare team.
RISK: NIPT compared to the Combined-Screening Test
One of the biggest drawbacks of the combined screening test on the NHS is the considerably higher “false positive” and “false negative” rates when compared to the results of an NIPT test. This means there is a higher chance of you receiving an erroneous result.
The false positive rate is where a healthy baby is wrongly identified as having a chromosomal abnormality i.e. wrongly identified as having Downs’, Edwards’ or Patau’s.
The false negative rate is the chance of a negative test result being given when in fact the condition being looked for is present; e.g. there was a low-risk score given for Down’s Syndrome, when in fact the baby has Down’s syndrome.
Universities Carry Out Large Study on 15,000 women
In one breakthrough study comparing the accuracy and efficacy of NIPT vs “standard screening” in 15,000 pregnancies; an NIPT test identified all 38 babies with Down’s Syndrome correctly (100% detection rate), whereas the standard screening test only identified 30 of 38 babies (78.9%) affected.
This means that 8 babies who did have Down’s syndrome were incorrectly reported as not having the condition by the standard screening test used by the NHS – so-called “false negatives”.
In the same research study, it was found that an NIPT test was wrongly positive in only 9 pregnancies that did not have Down’s Syndrome. Based on these 15,000 results, NIPT has a false positive rate of just 0.06% (a lot less than 1%).
The standard screening test, on the other hand, was positive in an alarming 854 pregnancies that did not have Down’s Syndrome. This equates to a false positive rate of 5.7% of pregnancies.
This means 854 (5.7%) parents would have been recommended to proceed with unnecessary invasive tests such as Amniocentesis or CVS, despite the baby not having Down’s Syndrome.
Why Are Women Hesitant to Take Invasive Tests?
With 1 to 2% chance of a miscarriage occurring during invasive tests such as Amniocentesis or CVS (chorionic villus sampling), it’s no wonder many new mums-to-be (and experienced mothers) are hesitant to proceed with an invasive diagnostic test and the experience of having to undergo a potentially painful procedure with a needle being introduced into the womb where their precious baby is growing.
It is for this reason that many women opt to have NIPT as a first choice of screening or when they have been given a high-risk result prior to proceeding with an invasive diagnostic test– NIPT is a superior choice to combined screening.
It is a non-invasive test (a simple blood test) where there is no risk of miscarriage and no harm to your baby.
SPEED: NIPT compared to the Combined-Screening Test
The combined screening test is an ultrasound scan combined with a blood sample and the results can take 3 – 14 days to come back to you.
Can’t wait 2 weeks for your results? With the advancements in NIPT screening in recent years, you can now expect results in as early as 5 working days from the date of your test.
Want to discuss NIPT, is it the test for you?
If you are considering taking NIPT for more clear and quicker answers, and would like more information on NIPT options available to you; our NIPT advisors would love to hear from you.