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Article Date: 19 Oct 2011 - 9:00 PDT Current ratings for:
New Blood Test For Down Syndrome - During Early Pregnancy
For years doctors have struggled to identify Down Syndrome in pregnant women, giving expectant mothers the opportunity to abort the full term. Now a new blood test promises to change all that with several new products coming to market that aim to provide accurate results in the 8th to 12th weeks.
Until these tests become commonly used and proved, women have to rely on an ultra sound that gives only risk indications. If the Sonographer finds indications of higher than normal risks, the mother has to undergo invasive tests, that not only put her under stress but subject her to a medical procedure at a delicate time in her term.
Prior to the new tests the only way to identify Down Syndrome was by capturing DNA from the fetus using a needle procedure called amniocentesis, that can't be done until well into the second trimester and another method known as chorionic villus sampling, which collects tissue samples from the placenta. Both have a small but real risk of miscarriage and obviously require a highly trained, experienced and skilled practitioner that may not always be easily available; adding to the mother's stress.
Down syndrome slows mental and physical development, and individuals with the syndrome usually show mild to moderate disability in intellect and skills for everyday living. Physically, they often have a flat face with a short neck and smaller hands and feet. They're at risk for complications like heart defects and hearing problems. Life expectancy is about 60 years.
Dr. Mary Norton, a Stanford University professor of obstetrics and gynecology clarifies :
A diagnosis before birth can pose a difficult challenge for couples as they decide whether to continue the pregnancy. It's not only about child-rearing, but also about what happens as the child grows into an older adult and may need care that the aging parents struggle to provide.
But parents who have gone the full term either by choice or unknowingly, assert their children have grown into valuable and intelligent adults in their communities, despite some minor social and psychological difficulties.
Two California based corporations, Sequenom Inc. and Verinata Health Inc., intend to offer the new tests to doctors in the United States by April 2012. They say it could be done accurately in the first trimester, with Sequenom at about 10 weeks, and Verinata as early as eight weeks. Results would be available 7 to 10 days afterwards. Another player, LifeCodexx AG of Germany says it will start offering its test in Europe by the end of the year, to be performed at 12 to 14 weeks initially. None of the companies would discuss costs.
Written by Rupert Shepherd
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today
MLA
5 Aug. 2012.
Please note: If no author information is provided, the source is cited instead.
posted by Jenny on 10 Nov 2011 at 12:11 am
The research led by Jacob Canick, PhD, and Glenn Palomaki, PhD, of the Division of Medical Screening and Special Testing in the Department of Pathology and Laboratory Medicine at Women & Infants Hospital and The Warren Alpert Medical School of Brown University, examined nearly 1,700 pregnancies at high risk of chromosomal abnormalities, 212 of which were affected by Down syndrome.
The newer test identified 98.6 percent of the Down syndrome pregnancies, while only 0.2% of the normal pregnancies were mistakenly called positive.
On a larger scale, take a group of 10,000 pregnant women for example. There will statistically be 20 cases of Down syndrome in this group when all is said and done.
If all 10,000 took the current screening tests, 500 are identified as potentially "positive" offered invasive diagnostic testing for further chromosome analysis.
Eighteen of the 20 Down syndrome cases will be among those 500 women who have an invasive procedure.
However, 482 of these 500 women who are having a normal pregnancy underwent an unnecessary invasive procedure.
More significantly, two procedure-related losses would be expected among these 482 women.
With the new DNA-based test, only the 18 affected pregnancies plus five of the normal pregnancies would now be offered an invasive procedure. All 18 Down syndrome cases would still be correctly identified.
“If this new test is used as we’ve described, nearly all women with a normal pregnancy could avoid an invasive diagnostic procedure and its associated anxiety, cost, and potential for fetal loss, " says Palomaki.
Recap : WITH THE NEW TEST ONLY 5 OUT OF 10,000 WOMEN WILL BE OFFERED AN INVASIVE PROCEDURE.
The blood test is accurate in detecting Trisomy 21, the genetic chromosomal abnormality that most commonly causes Down syndrome, 99.1 percent of the time as early as 10 weeks into a pregnancy.
Recent published data indicate that the core technology which underlies the MaterniT21 test also has the capability to detect other aneuploidies, such as trisomy 18 and trisomy 13.
If either of these aneuploidies is detected by the MaterniT21 test, Sequenom CMM will be reporting these results to the physician.
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