15 August 2016
Director, Antenatal Results and Choices (ARC); Professor of Genetics and Fetal Medicine, UCL Great Ormond Street Institute of Child HealthAppeared in BioNews 864
At the time of writing we still await a ministerial decision on the UK National Screening Committee (NSC) recommendation (1) – made back in January – to implement NIPT, non-invasive-prenatal-testing or cell-free DNA testing, into the current NHS antenatal screening programme for Down's (trisomy 21), Edwards' (trisomy 18) and Patau's (trisomy 21) syndromes. In the meantime, there has been much media interest and discussion about the proposal, with many advocates for those living with Down's syndrome expressing concerns on ethical grounds. The Nuffield Council on Bioethics has coincidently set up a working group to examine the ethics of NIPT from all perspectives (2), which will report later this year.
The NHS screening programme for Down's syndrome was established in 2001 to standardise the serum screening that was already being offered. With advances, the performance of the programme has improved, and the first trimester combined test now offers detection rates of around 85 percent for a three percent false-positive rate. However, the positive predictive value of current screening remains around five percent. This means that the majority of women with an increased chance of having a baby with Down's syndrome will learn that the baby does not have the condition when they undergo definitive diagnosis by invasive testing, with its associated small risk of miscarriage.
So, what are women in the UK doing now? Uptake of Down's syndrome screening varies across the country, with an average of around 65 percent of women in England choosing screening. The other 35 percent either believe their risk is low or do not want to know whether their fetus has Down's syndrome. Among women who accept screening and are found to have a chance of >1 in 150, only around half undergo invasive testing, often because they don't want to put their pregnancy at risk.
The evidence presented to the UK NSC to inform the recommendation on NIPT came from an evaluation study carried out by the RAPID team (3) and a systematic review undertaken by Warwick University (4). Having examined both submissions, and after a three-month public consultation, the committee concluded that introduction of NIPT could improve the current Down's syndrome screening programme for a minimal cost. There were caveats – it was agreed that the performance of the test was not as good for trisomy 18 and 13, and there remained question marks around the number of failed or inconclusive test results at the population level. So the UK NSC recommendation is a pragmatic one – NIPT is to be offered to women who, after the standard current screening, fall within the current threshold for the offer of further testing (>1 in 150 chance of trisomy 21, 18 or 13). The proposed plan is for a staged roll-out, following delivery of education to health professionals, with ongoing evaluation to monitor what happens in practice.
Key questions include whether NIPT raises any new ethical concerns that are different in scope to those raised by standard screening, and whether these might be mitigated by ensuring NIPT is introduced in a cautious way, as proposed by the UK NSC. One of the fears expressed by some commentators is that offering a safe, easy and non-invasive screening test may result in a higher uptake, more Down's syndrome pregnancies detected, and a subsequent rise in the number of terminations of pregnancy. Indeed, published evidence suggests a significant increase in testing when NIPT was available to the group with a higher chance of Down's syndrome as an initial alternative to invasive testing (3).
How far this will affect rates of termination for Down's syndrome is unclear. In the UK evaluation study, which offered NIPT as a contingent test, although more Down's syndrome cases were detected, only 83 percent of pregnancies were terminated (3) compared with the national Down's syndrome registry figure of 91 percent before the advent of NIPT (5). This means that introduction of NIPT may not significantly reduce the live birth rate. While we cannot forecast with absolute certainty how NIPT will influence women's choices, research projects both in the UK and the US found evidence to suggest some women will use NIPT results for information only (3,6). In other words, there are women who would opt out of the current screening programme because they do not want to make a decision about invasive testing. However, they would consider screening if NIPT were available as an alternative. This suggests that a proportion of women will use NIPT to prepare themselves and their families accordingly. Furthermore, as Down's syndrome is a recognised cause of late stillbirth, we must also consider the preventative benefit NIPT may confer through the detection of these pregnancies, which can then be more closely monitored in late gestation.
Critics of NIPT highlight that, currently, women do not always make informed choices at all stages of the NHS antenatal screening process. NIPT could exacerbate this problem by adding another step in the pathway and more information for midwives to impart and discuss in pre-test consultations. Undoubtedly, ensuring that every pregnant woman who opts into screening for trisomies is fully aware of what the possible outcomes might mean for her is very challenging, but evidence suggests that using the staged approach recommended by the UK NSC allows more opportunities for discussion and reflection, and has potential to ensure women and their partners make choices that are right for them at that particular time. From our experience at Antenatal Results and Choices (ARC) (7), we know that many women enter screening hoping to be reassured, and prefer to make decisions in a stepwise manner as and when those decisions become relevant to them. Of course, the vast majority will be reassured. What we also know is that, with well-coordinated supportive care, those women for whom screening leads to further (and often difficult) decisions are able to make the choices that are right for them.
For some Down's syndrome advocates, the arrival of NIPT has provided the impetus for questioning the very existence of standardised screening for Down's syndrome (8). Some maintain that the high termination rate after prenatal diagnosis is not the result of women making a valid decision based on their individual circumstances, but of women making a choice based on inaccurate information about the condition, or because of a pro-termination bias among their healthcare team. Contrary to this, our experience at ARC with women and couples after diagnosis suggests they are neither coerced nor ill-informed and they act autonomously.
In the heat of what has become an intense debate, we can lose sight of the main issue here. A central tenet of prenatal testing is to promote reproductive autonomy by providing women with information that can assist in pregnancy management. Bringing NIPT into the NHS will improve an established screening programme. Firstly, it will benefit pregnant women by helping them avoid procedure-related pregnancy loss and improve the care we deliver to women who know or expect their baby to have Down's syndrome. Secondly, it will improve equity by enabling women to have access to higher quality screening that is currently only available to those who have the means to pay for it. Importantly, access to screening will be enhanced. Research has shown that women overwhelmingly welcome a test that is safe, accurate, can be conducted early in pregnancy and reduces the need to consider invasive testing. We hope that the ministerial sign-off is imminent, and the detailed work to roll out an improved programme with the education and infrastructure required can finally get underway.