The population impact of screening for Down syndrome
Research type
Research Study
Full title
The population impact of screening for Down syndrome: an annual review of invasive diagnostic tests in England and Wales
IRAS ID
118949
Contact name
Joan Morris
Contact email
Research summary
In 2007, the National Screening Committee recommended that all pregnant women should be offered screening for Down syndrome using any test that has at least a 75% detection rate for a 3% false positive rate. A 3% false positive rate means that of all women who DO NOT have an affected pregnancy 3% will be informed that they are at an increased risk of a Down syndrome pregnancy and will be offered an invasive diagnostic procedure. Chorionic villus sampling (CVS) and amniocentesis procedures carry a risk of miscarriage of approximately 0.5% to 1%. Women may also be offered an invasive diagnostic procedure if screening suggests the presence of Edwards or Patau syndrome. It is therefore important to monitor the number of women who are having these procedures.
Recent reports on maternal plasma DNA sequencing methods indicate that they can achieve detection rates of about 98% with false positive rates of about 0.2% and with test failure rates between 3% and 7%. At present the cost of the tests is high and therefore the numbers of women having such tests is likely to be small. However the costs are certain to fall and it is essential that their introduction into clinical practice is carefully monitored. Of concern is the failure rate; if women with a failed test proceed to an invasive diagnostic test, the numbers of such tests will increase. It is therefore important to set up a system to monitor the number of women having these tests.
Data from women who had an invasive procedure will be analysed to determine how many were performed for each fetus with Down, Edwards or Patau syndrome detected; whether the ratios differed according to reason for the diagnostic test; and how accurate the prediction of risk of Down syndrome given at screening was.
REC name
London - Camberwell St Giles Research Ethics Committee
REC reference
13/LO/1054
Date of REC Opinion
29 Jul 2013
REC opinion
Favourable Opinion