Thursday, 26 April 2007

Report on Antenatal Down Syndrome Screening released by the National Screening Unit

Antenatal Down Syndrome Screening in New Zealand 2007 is the result of work carried out by the Antenatal Down Syndrome Screening Advisory Group, which was convened as part of a review of the current practice of antenatal screening for Down syndrome undertaken by the National Screening Unit.

The Advisory Group unanimously agreed that the current practice of screening using only maternal age and/or nuchal translucency (NT), without biochemical markers is unsafe, inequitable, and should not continue. The Advisory Group made a number of recommendations for ways to improve the safety and quality for antenatal Down syndrome screening.

Advisory Group Chair Dr Paul Harper says current screening methods commonly used are not as reliable and accurate as other methods that are available. This results in too many women having diagnostic tests, and as these have a small risk of miscarriage (about 1 to 2 percent), pregnancies are being lost unnecessarily.

National Screening Unit Manager Karen Mitchell says the Advisory Group had a difficult task, given the wide range of views represented and the need to consider the technical, social and ethical issues of antenatal Down syndrome screening. The Minister of Health, Hon Pete Hodgson, has requested further work to be carried out to look at how a nationally organised screening programme for antenatal Down syndrome could be implemented.

Mitchell said that the primary intention of a national screening programme would be to improve the quality and safety of screening practice.

“The key driver is to improve the safety and quality of screening practice for women in New Zealand. The work of the Advisory Group provides a clear way forward to do this,” she says.

“A national screening programme would include an informed consent process, national standards, monitoring and evaluation. The National Screening Unit will continue to work with key stakeholders including colleges, health care providers and the New Zealand Down Syndrome Association as it carries out this work.”

Mitchell said the further work requested by the Minister would be completed by October 2007.

Download a copy of 'Antenatal Down Syndrome Screening in New Zealand 2007'

For further information contact:

Michael Flyger
Media Advisor
Ministry of Health

Ph: 04 496 2265
Mobile: 0274 346 878

--------------------------------------------------------------------------------

Questions and Answers

Why was the Advisory Group establised?

International research indicates that safer and more reliable tests could be used in New Zealand to screen for Down syndrome. The tests currently used can result in women being unnecessarily referred for an invasive diagnostic procedure, for which there is a small risk of miscarriage (1 to 2 percent).

There are better methods of screening that can be implemented, and these should be accompanied by high quality information, a robust informed consent process, audit, monitoring, and evaluation.

What did the Advisory Group do?

This Advisory Group considered the technical, medical, social and ethical issues relating to screening. The Advisory Group developed its advice over an intensive six-month period and completed its report to the National Screening Unit in January 2007.

Who was on the Antenatal Down Syndrome Advisory Group?

Members of the Advisory Group were appointed for their expertise and experience. It included:

What were the recommendations of the Advisory Group?

The Advisory Group unanimously agreed that the current practice of screening using only maternal age and/or NT, without biochemical markers is unsafe, inequitable, and should not continue. However, there was not unanimous agreement on the best way of addressing concerns about current practice. The Advisory Group made 29 key recommendations.

What else has been done to look into this issue?

The National Screening Unit contracted Professor Peter Stone (Head of Department of Obstetrics and Gynaecology, University of Auckland) to undertake a project to assess the current practice of antenatal screening for Down syndrome in New Zealand, and advise on future delivery of antenatal screening for Down syndrome. Professor Stone delivered his report in early February 2006. Amongst other things, Professor Stone recommended “that the current situation of age and Nuchal Translucency screening leading to invasive testing be urgently reviewed with the view to stopping this as a screening practice”.

The National Screening Unit also commissioned a systematic review of the literature. This review is available at:
http://nzhta.chmeds.ac.nz/publications/downs.pdf

What have the Ministry and the Minister decided?

The Minister of Health has considered the report of the Advisory Group and has asked for more detailed work to be carried out to determine how a nationally organised programme for antenatal Down syndrome could be implemented in New Zealand.

What steps have already been taken to improve current screening practice?

In 2006, the Ministry of Health wrote to relevant health professionals and services, advising them of the concerns and providing advice on the safest forms of screening available in New Zealand.

Requirements have also been placed on practitioners performing Nuchal Translucency ultrasounds scans. From 1 July 2007, all health professionals performing these scans under the Section 88 Maternity Services Notice must have the appropriate training and use appropriate equipment. They will be required to be have obtained the appropriate accreditation recognised by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists and the Royal Australian and New Zealand College of Radiologists.

Will a national screening programme be introduced?

This is a complex area. Before a decision is made, a great deal of detailed work needs to be carried out to look at how a programme could be implemented.

When will a decision be made about whether a national antenatal Down syndrome screening programme will be introduced?

Advice on how a programme could be implemented will be provided to the Minister of Health by 30 October 2007.

What is a national screening programme?

A national screening programme ‘organises’ all element of the screening and diagnostic pathway. At a national level it includes planning, co-ordination, monitoring and evaluation of all activities along the screening pathway to make sure the services are safe and of high quality.

What would be the advantages of a national screening programme?

Implementing a national screening programme would help to ensure that women who choose to have screening are offered the safest and most reliable form of screening possible. It would also help to ensure that invasive diagnostic procedures are limited to women who have an increased chance of having a child with Down syndrome and who have made an informed choice to use those tests.

Implementing a ‘best practice’ form of screening is complex and involves co-ordinating the activities of a range of health practitioners over two trimesters of pregnancy. It needs to be implemented in a co-ordinated and nationally consistent manner, with robust quality assurance processes. The structures of a national screening programme could help the sector to implement ‘best practice’. 

Would a national programme mean that screening for Down syndrome is compulsory?

No. All national screening programmes are based on consumers giving informed consent to the screening and diagnostic pathway. Women would be able to decline screening, decline diagnostic tests, and make their own decisions about their pregnancy. Women would need to be offered access to appropriate counselling and support services.

What is Down syndrome?

Down syndrome is a life-long condition that causes delays in learning and development. It is caused by the presence of an extra copy of chromosome 21 (i.e., three instead of two). This is also called trisomy 21. Down syndrome occurs in approximately one in seven hundred pregnancies, and about seventy children are born with Down syndrome each year in New Zealand. For more information about Down Syndrome see the New Zealand Down Syndrome Association website.

What is the purpose of antenatal screening for Down syndrome?

The purpose of antenatal screening for Down syndrome is to provide pregnant women, who choose to have the screening tests, with information about whether the fetus is likely to have Down syndrome or some other fetal anomaly. This information may help women to make informed decisions and plans about their pregnancy, including:

• whether to have diagnostic testing
• whether to continue with or terminate the pregnancy
• preparing for the birth and life of a child with Down syndrome or other condition
• planning to give birth at a specialist centre that can provide any immediate neonatal treatment, if necessary.

What is a screening test?

A screening test is offered to people who do not have any symptoms or signs that they have a particular condition. It predicts the likelihood of a person having or developing a particular condition. With antenatal screening for Down syndrome, screening tests can identify pregnant women whose fetus have an increased risk of Down syndrome and who might benefit from further investigation. These women are offered a diagnostic test (discussed further below).

Are screening tests 100 percent accurate?

Screening tests cannot tell you whether the fetus does have Down syndrome. Screening tests sort women into two groups: women who are low-risk and do not have an increased chance that their fetus has Down syndrome, and women who are high-risk and do have an increased chance that their fetus has Down syndrome. There will be some false-negative results and some false-positive results.

What is a diagnostic test?

A diagnostic test states if the condition definitely is present or not. Diagnostic tests are often expensive and carry risks. The use of these tests should be limited to women who have an increased risk of having the condition.

What screening tests for Down syndrome are currently used in New Zealand?

• Advanced maternal age: women aged over 35 years are offered a diagnostic test. Screening on the basis of maternal age results in significant numbers of women being referred for diagnostic tests, which carry a risk of fetal loss. Maternal age screening means that women who are less than 35 years of age are advised they have a low risk, and are not offered other forms of screening or diagnostic tests. Although older women are more likely to have a child with Down syndrome, more children with Down syndrome are born to younger women due to the fact that there are more births in this age bracket.
• Nuchal translucency (NT) ultrasound scan: currently all women consulting a health practitioner in their first trimester of pregnancy can be offered a nuchal translucency ultrasound scan, which receives public funding. The screening test involves measuring the depth of fluid at the nape of the fetal neck. The test is performed during an early ultrasound scan (11-14 weeks of pregnancy). An increased amount of fluid may indicate that the fetus has Down syndrome or another chromosomal, structural or genetic anomaly. NT scans should only be performed by highly skilled professionals. From 1 July 2007, practitioners performing NT scans under the Section 88 Maternity Services Notice will need to be accredited by a recognised organisation.
• Maternal serum screening: Women who do not consult a health practitioner in their first trimester of pregnancy can have a second trimester maternal serum screening test. This test is not publicly funded. It costs approximately $75 and is available from LabPlus (Auckland DHB). It involves taking blood from the woman at 14-20 weeks of pregnancy and measuring the concentration of various biochemical markers in the blood.

What is the age-related risk of having a child with Down syndrome?

Levels of risk of having a Down syndrome pregnancy in relation to a woman’s age

Why are the newer methods of screening for Down syndrome better than using maternal age?

If 50,000 women were screened on the basis of maternal age, approximately 20 percent of them (i.e. 10,000 women) would be considered high-risk and would be offered a diagnostic test. The diagnostic test has a 1 percent risk of miscarriage. If we screen 50,000 women on the basis of their maternal age, we could expect this to result in 100 miscarriages.

However, if the most reliable form of screening is used to screen 50,000 women, the 20 percent of women offered diagnostic tests could be reduced to around 1 percent (i.e. 600 women). Instead of 100 miscarriages we would expect to have about 6 miscarriages.

What diagnostic tests for Down syndrome are currently used in New Zealand?

Approximately 3,500 diagnostic tests are currently performed each year in New Zealand. These procedures carry a risk of miscarriage (1-2 percent).
Amniocentesis: an invasive procedure whereby a sample of amniotic fluid is removed and sent for analysis.
Chorionic villus sampling (CVS): an invasive procedure where placental tissue is removed and sent for analysis.