Non-invasive prenatal testing for Down syndrome is feasible, acceptable to parents, and could be introduced into the National Health Service (NHS), researchers in the United Kingdom say.
The results of a National Institute for Health Research (NIHR) study carried out by the first NHS laboratory to provide non-invasive prenatal testing testing were reported to the annual conference of the European Society of Human Genetics Saturday.
Presenting the findings, Professor Lyn Chitty, from the University College London Institute of Child Health and Great Ormond Street Hospital, London, evaluated the possibility of introducing non-invasive prenatal testing into the NHS screening program for Trisomy 21 (Down syndrome). The researchers will present their study to the UK National Screening Committee later this month and hope that it will inform their decisions on if and how to implement non-invasive prenatal testing in the NHS.
As part of the study, carried out by the NHS laboratory at Great Ormond Street Hospital, women at high and medium risk of having a child with Down syndrome were offered non-invasive prenatal testing, and over 2,500 undertook the test.
Prof Chitty says, "There was a very high uptake of testing and we saw invasive test numbers fall sharply. NIPT performed well in identifying problems, and women were very positive about it. The cost of providing an NIPT service will depend on the cost of the test itself and how it is implemented. There will be significant savings resulting from a decrease in invasive testing whilst increasing the detection of affected babies. The reduction in invasive testing also means there will be a reduction in miscarriages and loss of unaffected babies which is much better for parents."
Reporting the results of a second study from the same group, Dr Suzanne Drury, a translational research and development scientist from Great Ormond Street Hospital, will describe the team's experience in the use of NIPD (non-invasive prenatal diagnosis) to diagnose the disorder congenital adrenal hyperplasia (CAH). CAH exposes a female fetus to male hormones, which can result in the development of masculinised external genitalia. It is an autosomal recessive (AR) disorder, in which the defective gene must be passed on from both parents in order to cause disease.
"We chose CAH because the gene that causes it is particularly challenging to study. It is the most common adrenal disorder in childhood and affects one in every 18,000 live births. In the UK, NIPD for fetal sex determination is carried out for an average of 13 pregnancies per year at risk of CAH because it is the female fetuses that are at risk.
"Fetal sex determination allows targeting of invasive testing to see if the female fetus is carrying two mutant copies of the CAH gene and is therefore affected. As we were already carrying out NIPD for sex determination, and there is a potential in utero treatment for CAH available, we felt that this was a good condition to select to allow treatment to be very specifically targeted to only those female fetuses that are affected."
In 2014, the researchers say, 32% of prenatal diagnostic tests for monogenic disorders in their laboratory were non-invasive. NIPD for single gene disorders in a fetus is diagnostic, as it targets specific genetic changes present in a high risk family.
For this reason it will remove the need for invasive testing completely, reducing the risk of miscarriage and making prenatal diagnosis for these conditions safer and more accessible to families who would not otherwise be prepared to take the risk.