Home / Health / Fetal DNA tests infer rarely accurate though experts advise of exceptions

Fetal DNA tests infer rarely accurate though experts advise of exceptions


CHICAGO (Reuters) – A Roche blood exam to shade fetuses for Down syndrome worked distant improved than customary prenatal screening tests in younger, low-risk women, U.S. researchers pronounced on Wednesday, environment a theatre for some-more widespread use.

The new study, published in a New England Journal of Medicine, is a largest to uncover a tests are accurate in even low-risk women. But experts warned that women who exam certain still need to endorse a outcome by some-more invasive evidence contrast such as amniocentesis, generally if they would cruise terminating a pregnancy.

“This is a good exam for detecting Down syndrome though it doesn’t detect everything, it isn’t diagnostic, and it doesn’t always work to yield a result,” pronounced Dr. Mary Norton of a University of California, San Francisco.

Prior studies have shown such fetal DNA tests, that magnitude DNA fragments from a placenta present in a mother’s blood, are rarely accurate during detecting Down syndrome and dual other chromosomal abnormalities in high-risk women, typically those over a age of 35.

Several physicians’ organizations have upheld use of a newer dungeon giveaway fetal DNA tests over a customary screening in older, high-risk women.

Norton and colleagues tested scarcely 16,000 women who had an normal age of 30. The researchers compared Roche’s Harmony exam to customary prenatal screening for Down syndrome – that relies on biomarkers in a blood and a fetal ultrasound – in a same organisation of women.

The Roche exam identified all 38 cases of Down syndrome compared with 30 rescued by customary screening. The fake certain rate for a new fetal DNA exam was 0.06 percent of a investigate race contra 5.4 percent for customary screening.

But there were still 9 fake certain formula in a organisation that got dungeon giveaway fetal DNA screening.

In addition, in scarcely 500 women a fetal DNA exam was not means to broach any outcome given there was not adequate fetal DNA in a profound women’s blood. Further testing, however, showed that some 2.7 percent of fetuses had chromosomal defects, including those that could not have been rescued by a new fetal DNA technique.

More than 1 million fetal DNA tests have been achieved given 2011. One of their advantages is that if women exam negative, they can equivocate carrying an invasive evidence test, that can means miscarriages in roughly 1 in 600 women.

But a newer tests are not regulated by a U.S. Food and Drug Administration, and companies are heavily compelling their opening in ways that competence trick patients, critics say.

In a minute published in a New England Journal of Medicine, Ankita Patel and colleagues from Baylor College of Medicine and a Chinese University of Hong Kong advise that women should not confirm to cancel pregnancies formed on such screenings alone.

They cited their possess work that collected information on 307 women who screened certain on fetal DNA tests. The formula enclosed 56 fake positives, definition a child did not have Down syndrome or a dual other common abnormalities (trisomy 13 and 18) prisoner by a tests.

In some cases, women had already scheduled an termination tentative amniocentesis results, a exam given between 15 and 20 weeks of pregnancy. Even when that evidence valid a child did not have those abnormalities, some women questioned either a screening outcome was some-more reliable.

“They consider it is a evidence exam given it’s genetic,” Patel pronounced of a fetal DNA tests.

CONFUSION AMONG DOCTORS

Another reason for a difficulty is a fast introduction of this new technology. Many doctors are still only training about it, pronounced Dr. Michael Greene, arch of obstetrics, Massachusetts General Hospital in Boston, who was not concerned in a research.

He also points to companies’ assertive selling of their tests on a Internet. Ariosa Diagnostics, acquired by Roche in January, says a Harmony exam for fetal chromosomal abnormalities offers “clear answers to questions that matter,” earnest “accurate formula from as early as 10 weeks of pregnancy.”

Rival Sequenom Inc says on a website that it offers evident results: “There’s no room for maybe.” Other companies charity such tests embody Illumina and privately-held Natera.

Greene pronounced many women are not wakeful that these tests are not evidence and association disclaimers are not easy to find.

Both Sequenom and Ariosa pronounced they suggest medical providers warn their patients that a screening exam is not a deputy for a evidence test.

The FDA is weighing either to umpire such tests. Patel believes a slip competence assistance given a tests “would have some-more disclaimers so women know what they are removing into.”

(Reporting by Julie Steenhuysen; Editing by Michele Gershberg and Diane Craft)

Article source: http://www.reuters.com/article/2015/04/02/us-health-prenatal-tests-idUSKBN0MT00P20150402

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