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Improved blood test for Down's syndrome

By Tim Sandle     Apr 7, 2015 in Science
San Fransisco - A new method for testing pregnant women's blood for disorders in unborn children promises major advances in diagnostic medicine, according to a new study.
A team of U.S. based researchers (University of California, San Francisco) have stated that Down's syndrome can now be reliably tested for in the mother's blood, according to the BBC. This improve method will raise policy as well as ethical questions, as to what tests a mother wishes to have once she falls pregnant.
In the U.K., for example, whether a woman can have a test to see if her unborn child has Down's syndrome is only permitted after an assessment of the age of the woman and then whether an ultrasound scan suggests any kind of risk. and even here the tests conducted were not totally accurate. Moreover, such tests are invasive and they involve using a needle taking a sample of the placenta or the fluid that bathes the baby. Concerningly, this test carries a risk of miscarriage.
The newly devised blood tests examine for fragments of DNA from the placenta, which can drift about in the mother's bloodstream. The tests are said to be more accurate than those previously available. In trials, the new method correctly identified 38 cases of Down's syndrome from some 16,000 women who were tested. This was a diagnostic study, which compared a new antenatal screening test with standard screening for three genetic conditions, including Down’s syndrome.
Down syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21 (this occurs when people inherit three copies of chromosome 21 instead of the usual two). A chromosome is a single piece of coiled DNA containing many genes. The chromosome encodes most of a person’s genetic information. This extra bundle of genetic information can be detected in the blood.
The new test has been described in the New England Journal of Medicine, in a paper headed "Cell-free DNA Analysis for Noninvasive Examination of Trisomy."
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