The triple test assesses the risk of having a Down's baby based on:
Serum is taken from 15-20 weeks gestation, ideally 16 weeks. A high hCG, low AFP and low oestriol suggest a Down's child. Results are expressed in terms of the risk of having a Down's child eg. 1 / 145. Detection rates range from 45-65% with a 5% false positive rate. Those with a risk greater than 1 in 200 are offered amniocentesis.
Other risks may also be detected eg. a high AFP suggests a neural tube defect.
Improved combined methods of screening are now available and women should not be offered the triple test in the UK.
Note that the triple test was known as the Barts test in some areas.
The recommended method of screening for Down's syndrome is using the Combined Test. Combined screening can be carried out in the first trimester and up to 14 weeks and 1 day of pregnancy.
Women who present too late for combined screening should be offered quadruple testing in the second trimester of pregnancy.
For more information: NHS Fetal Anomaly Screening Programme (NHS FASP) www.fetalanomaly.screening.nhs.uk
References:
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