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A new test, based on DNA blood, has been found to be more efficient in detecting Down syndrome in unborn children than other investigative methods for this genetic disorder, according to researchers.
The test showed perfect accuracy in a clinical trial, exposing Down syndrome in all the 38 women whose unborn children had inherited the disorder, announced a report published on April 2 issue of the New England Journal of Medicine.
Standard screening methods managed to detect the Down syndrome in only 30 of the 38 future mothers. In the new test, scientists researched fetal DNA which is present in a pregnant woman’s bloodstream. Greater quantities of this fetal DNA in a woman’s blood, say the doctors, is a clear indication that her unborn child is suffering from Down syndrome.
“It is clearly a better test than what we’re currently using. If one is looking at screening specifically for Down syndrome, there’s no question this test is better for that purpose,” said study lead author Dr. Mary Norton, a professor and vice chair of clinical and transitional genetics at the University of California, San Francisco.
Experts recommend that even in the case of a positive result, mothers should take an invasive diagnostic test, like amniocentesis, before taking any measures regarding their pregnancy.
Down syndrome is a disease that happens when a baby has an extra copy of chromosome 21 in its DNA. The birth fault can cause intellectual and physical disabilities, but also other health problems, as well.
Until now, screening for Down syndrome was usually done by taking a blood test and an ultrasound early in the pregnancy. The U.S. Centers for Disease Control and Prevention explains that the blood test is a good indicator for patterns of specific substances in a mother’s blood which are connected with chromosomal problems that cause Down syndrome. The ultrasound examines the body of the fetus for indications of birth defects.
The clinical trial involved a cell-free DNA screening test, which must be carried out at 10 to 14 weeks of pregnancy. The new test has been available since 2011.
Cell-free DNA tests have been used before, but to check if older women present a higher risk for birth defects. More than 15,000 women over the age of 31 participated to the clinical trial.
Besides its excellent accuracy, the cell-free DNA test had a much smaller rate of false-positive results than regular screening — 0.06 percent versus 5.4 percent, the study authors said.
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