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A new blood test for Down ’s syndrome during pregnancy could reduce the routine of char who undergo further invasive examination to detect fetal freakishness , new research advise .
The test — which look for traces offetal DNA in the female parent ’s blood — is extremely accurate , and has a lower false positive rate than current method of testing , the cogitation found .
In some conditions of aneuploidy, including Down syndrome and Trisomy 18, an extra chromosome is present.
While the test has been usable since 2011 , it is not widely used , and few studies have pursue women forward over time to examine how the mental test would be incorporated into the care that patient role already receive .
In the new subject field , about 1,000 woman in England underwent the test , send for cell - freeDNA examination , at 10 weeks of pregnancy . They also had an sonography and a internal secretion analysis at 12 week , which are received masking method acting for observe fetal abnormities .
The research worker compare the unexampled test to the standard methods by look at how well each find cases of aneuploidy in fetuses . circumstance of aneuploidy , including Down syndrome , stanch from bear an abnormal act of chromosome .
final result showed that both the new mental testing and the stock showing methods observe all pillowcase of Down syndrome , Edwards syndrome ( Trisomy 18 ) and Patau syndrome ( Trisomy 13 ) .
But the cellular phone - gratis DNA testing had a much lower fictitious positive rate : 0.1 percentage , compare with 3.4 per centum for standard screening methods . Because all positivistic screening tests need to be affirm with invasive testing — either amniocentesis or chorionic villus sampling , procedures that have a small risk of exposure of causing miscarriage — the use of the cell - free DNA mental test reduces the number of invasive test , the researchers say .
The study is published today ( June 7 ) in the journal Ultrasound in Obstetrics & Gynecology .
Although jail cell - free DNA testing is very accurate , the test can not supervene upon current screening method for aneuploidy — it should be used in connective with these methods , said Dr. Mislen Bauer , theater director of genetic science and metabolic process at Miami Children ’s Hospital . Bauer said her institution started using the new test about six months ago .
The American Congress of Obstetricians and Gynecologists commend that the test be offered only to women at high risk of exposure of make tiddler with aneuploidy , include cleaning lady ages 35 and over and those with unnatural echography resolution .
But ACOG does not commend the mental test as part of routineprenatal screening . Few studies have examined the accuracy of the test in low-down - endangerment women , or those carrying twins or multiples , so it is not yet recommend for these groups , ACOG says .
Because the mental testing is a screening test , and not a diagnostic test , the results call for to be confirmed with amniocentesis or chorionic villus sampling , ACOG says . And a disconfirming exam result does not definitively rule out aneuploidy .
In about 4 to 5 percent of cases , there is too little foetal DNA in the blood sampling to obtain a result , and the run may require to be repeated .
