Non-invasive prenatal testing for Down's syndrome - beyond the hype

There has been much recent media interest in non-invasive prenatal testing for Down's syndrome (NIPT) (see BioNews 805), and this coincides with deliberations by the UK National Screening Committee on its potential inclusion in the NHS Down's syndrome screening programme.

The test itself is not so new in the UK. It first became available in the private sector in late 2012, and provision has since proliferated. Thousands of women have been willing to pay between £400 and £1,000 for the test since then. In fact, we can speculate that the recent dip in the number of invasive diagnostic tests performed after Down's syndrome screening is due to women having NIPT (1).

There is enough evidence in the literature, including from large-scale studies (albeit mainly in medium and high-risk populations), to conclude that NIPT is a highly accurate screening test for Down's syndrome, with higher sensitivity and specificity than standard NHS tests (2). In view of this, it is likely to be offered on the NHS as a contingent screen (offered to women who fall within a particular risk assessment after their primary Down's syndrome screening test). This will of course not happen immediately, but there are already several NHS trusts that have implemented NIPT at a local level (3). Suffice to say, NIPT is here to stay.

We at Antenatal Results and Choices (ARC), a UK charity that provides information and support to parents through antenatal testing and its consequences, can attest to the appetite for NIPT as we take numerous calls each day on our national helpline from women and their partners keen to gain the most accurate assessment of their risk of having a baby with Down's syndrome. Women clearly value having a test that will most often provide a result that means that they can avoid invasive diagnostic procedures that carry the risk of miscarriage.

However, the possible introduction of NIPT into a public health screening service has prompted ethical concerns. Some feel that because it involves no more than a simple blood test it will quickly become 'routinised' - women will hold out their arm blithely without thinking through the consequences. Some fear an increase in uptake, with an exponential rise in detection and then termination as women feel pressured to end pregnancies when given a diagnosis of aneuploidy. The author of a recent Washington Post online article was unequivocal: 'This will promote even more intensive de-selection of fetuses with Down syndrome, which in turn will negatively affect their position in society.' (4)

Our experience at ARC gives us confidence to allay some of those fears. While we do not know for sure what will happen when NIPT is available within the NHS, we can predict that the uptake of Down's syndrome screening nationally (currently around 66 percent) will increase. This will be partly due to more women opting-in because they feel decisions about invasive tests will be based on a more reliable evaluation of their individual risk. However, those for whom NIPT brings the news that the fetus is likely to be affected will still face the difficult decision about further testing. And it is not a given that all women will proceed to this next step.

We also need to be mindful that, however expectant parents receive a prenatal diagnosis, the decision about the future of a wanted pregnancy is never made lightly and will always be emotionally painful. We must always ensure that parents in this position receive high-quality care and non-judgmental support to enable them to proceed in a way that is right for them.

If we are confident that NIPT will improve detection rates, reduce the need for risky invasive procedures and achieve this in a cost-effective way, there is every reason to herald this technology as a welcome breakthrough. However, there are some caveats. The fact that NIPT has no risk to the pregnancy means that some women find it hard to give themselves permission to go directly for diagnostic testing, when their level of anxiety is such that they would really prefer to have a definitive yes or no answer. Furthermore, adding NIPT into the current screening programme creates an extra stage in the process, delaying the final diagnosis by a week or more. This will be a significant delay for women who decide to end their pregnancy and who would prefer to have the termination managed surgically rather than undergo medically induced delivery. The shortage of surgical expertise within the NHS means that this option is not available in most hospitals beyond 13 weeks. And, with fewer invasive procedures being undertaken, we will need to make sure that they are performed by clinicians who are able to maintain the requisite skills and competency.

My organisation is supportive of the NHS implementation of NIPT. It will end the current inequity, in which only those women who have means to pay benefit from the most effective screening. National oversight will ensure that provision is carefully co-ordinated and quality controlled. Fewer women will have to face the anxiety of invasive testing and the agony of losing a baby as a result of a diagnostic procedure. One thing NIPT will not change is the devastating impact of a confirmed prenatal diagnosis within the context of a wanted pregnancy, so we must be vigilant in employing the highest standards of care for expectant parents in this circumstance and support their individual choices.