Thursday, 2 April 2015

Newer Test for Down Syndrome Called 'Major Advance'


But it won't eliminate need for invasive diagnostics such as amniocentesis, doctors say

WebMD News from HealthDay

By Dennis Thompson

HealthDay Reporter

WEDNESDAY, April 1, 2015 (HealthDay News) -- A DNA-based blood test appears to be more effective in detecting possible Down syndrome in unborn children than other screening methods for the genetic disorder, researchers say.

The test exhibited perfect accuracy in a clinical trial, detecting Down syndrome in all 38 women whose children had inherited the disorder, the researchers report in the April 2 issue of the New England Journal of Medicine.

By comparison, standard screening methods only detected Down syndrome in 30 of the 38 expecting mothers, the study authors said.

In the test, clinicians analyze fetal DNA circulating freely in a pregnant woman's bloodstream. Greater quantities of fetal DNA -- also called cell-free DNA -- in a woman's blood are an indication that her unborn child suffers from Down syndrome, the researchers said.

"It is clearly a better test than what we're currently using," said study lead author Dr. Mary Norton, a professor and vice chair of clinical and translational genetics at the University of California, San Francisco. "If one is looking at screening specifically for Down syndrome, there's no question this test is better for that purpose."

Despite its accuracy, experts warn that mothers should follow up any positive result with an invasive diagnostic test such as amniocentesis before making any decisions regarding their pregnancy.

"Nobody wants a needle in their uterus when they can get a blood test, but that's just not the way it works in 2015," said Dr. Joe Leigh Simpson, senior vice president of research and global programs at the March of Dimes. "This [new test] is a major advance, but you're still going to have to confirm the results."

Simpson compared a positive result in a cell-free DNA test to a positive cancer screen. "We're not going to be treated for cancer on the basis of an X-ray. We're going to have a biopsy to find out what the situation actually is," he said.

Down syndrome occurs when a baby has an extra copy of chromosome 21 in its DNA. The birth defect can cause physical and intellectual disabilities, as well as lifelong health problems.

source : Newer Test for Down Syndrome Called 'Major Advance'

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