The likelihood ratio (LR) is the height to the affected distribution curve (d) divided by the height to the unaffected distribution curve (c). In figure a) at value x the LR will be less than 1.00 thus reducing the risk. In figure b) at value y, the LR will be greater than 1.00 thus increasing the risk. The calculator allows a user to enter in their maternal age at term and view their age-specific risk for having a baby with Down syndrome. Risk calculation for Down syndrome combines at least two factors in all cases: the risk of Down syndrome related to maternal age and the risk indicated by maternal serum markers. The maternal age-related risk at term used in each of the six software packages is given in Fig.
Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Down's Syndrome article more useful, or one of our other health articles.
Prenatal Screening for Down's SyndromeIn this article
It is important to emphasise that the decision to have any form of screening should be an informed one. Some people may decide against having diagnostic testing or even screening for Down's syndrome when offered the choice. It is important that appropriate information, counselling and support accompanies testing and screening.
Pre-screening discussion
Women should be given information regarding Down's syndrome screening at their first appointment with a healthcare professional. Operator manual abl 80 flex radiometer danaher. This should include:
Pre-screening probability
The risk of Down's syndrome varies with maternal age[1]: Ernie ball how to play guitar phase 1.
The risk also increases after a previously affected pregnancy:
Down's syndrome screening
Screening methods
Serum markers for Down's syndrome
These include:
Factors affecting the test
Adjustments are required to take account of the following factors :
If a woman has been screened for Down's syndrome or open neural tube defects in a previous pregnancy, the levels of the screening markers in that pregnancy can be used to adjust the marker levels in the current pregnancy. A woman with a false positive result in one pregnancy is likely to have a false positive result again in a subsequent pregnancy .
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The evidence base for the screening tests
A key study in Down's syndrome screening was the Serum Urine and Ultrasound Screening Study (SURUSS)[13, 14]. It compared the different prenatal screening tests available for Down's syndrome. It was a prospective study of about 47,000 singleton pregnancies conducted in 25 maternity units. It concluded that:
The screening policy has been subject to several reviews, which have altered the recommendations for the national programme[12]. Screening within the NHS must be cost-effective, easy to deliver and achieve the agreed targets.
There are a number of considerations given to recommending a screening test which is simple and practical to implement, is workable in the NHS, has lower service delivery risks, is acceptable to women, achieves the agreed standard and is also cost-effective compared to others.
The Integrated and Serum Integrated tests require women to have two serum tests on different appointments for the risk result to be generated. Rocky 1981 hindi movie mp3 songs free, download. Failing to attend the second appointment renders the test invalid and so there is a responsibility for busy healthcare professionals (usually a midwife) to trace defaulters and ensure they complete the screening cycle. There is a risk that the completion of the test will not occur and data cannot be correlated from one attendance to another. There is also a greater chance that results will be not be accurate because of the differing variables involved and that screening follow-up and closure of the screening on those women who change postcodes during the two appointments may not be achieved.
The result of the test is provided later in the pregnancy, limiting the timeframe for decision making. Equally, the more complex the process, the more likely it is that clinical errors will occur. Costs incurred from all strategies have been assessed, providing evidence that the combined test is more cost-effective whilst still delivering to the set standard.
The National Institute for Health and Care Excellence (NICE) guidelines for antenatal care have also looked at all available evidence for Down's syndrome screening[15]. NICE found that:
This led NICE to the conclusion that the combined test should be the screening test offered to women in the first trimester. This has good diagnostic accuracy for Down's syndrome and other chromosomal abnormalities.
Screening for Down's syndrome in multiple pregnancy
The futureDown Syndrome Screening Accuracy
The examination of fetal cells in the maternal circulation for prenatal diagnosis is currently being evaluated and may reduce the need for invasive tests such as chorionic villus sampling (CVS) and amniocentesis.
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Relative Risk Calculation
Related InformationDown Syndrome Risk Calculator
I agree that there is very little information about this condition. I was born with it and apparantly spent 2 months in an incubator. I would like more information on possible life long problems as a..
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