June 8, 2013
Simple Blood Test Is Less Invasive, More Precise Down’s Syndrome Test
redOrbit Staff & Wire Reports — Your Universe Online
According to Nick Collins, Science Correspondent with The Telegraph, currently pregnant mothers typically undergo a screening while undergoing their 12-week ultrasound scan.
This scan is used to determine the potential risk that the fetus will be born with the genetic disorder — a condition caused by the presence of an extra copy of chromosome 21.
“About 30,000 of the 600,000 women who give birth every year are deemed at high risk of having a baby with Down´s as a result, and are offered an invasive second test which comes with a one in 100 chance of causing a miscarriage,” Collins explained. However, the developers of the new blood test “claim their new blood test could reduce the number of women referred for the second test to 1,500 per year if it were offered routinely in Britain.”
During this screening, doctors measure the nuchal translucency, which is a pocket of fluid at the back of the baby´s neck, the BBC News Website Health Editor Caroline Parkinson said. Infants with Down´s syndrome are more likely to have more fluid than usual.
In addition, women are given a blood test that tests for abnormal levels of some proteins and hormones. They are then given a set of odds that their unborn child has the genetic condition.
Another process, chorionic villus sampling (CVS), involves testing a small sample of the placenta, while an amniocentesis tests the amniotic fluid around the baby. This test carries a one percent risk of miscarriage.
The new test is safer, more sensitive, and less likely to return a false positive, the researchers said.
“This test is nearly diagnostic. It tells you almost certainly your baby has Down's or almost certainly it does not,” professor Kypros Nicolaides, who is leading the research, told the BBC. “From a woman's perspective, that is a much more clear message about what to do next.”
According to The Telegraph, the test will be offered free of charge at two UK hospitals following a successful trial of more than 1,000 pregnant women.
As part of the trial, which is detailed in the journal Ultrasound in Obstetrics & Gynecology, blood samples were taken at ten weeks and sent to a US laboratory, where it was analyzed and returned to the UK within 14 days.
That time frame, the researchers said, allows women deemed to be high-risk to undergo a second test when they return for a 12-week ultrasound scan.
“Experts conducting the ongoing study say that, if offered right across the NHS, the method could spare tens of thousands of women the need for more invasive testing, and prevent almost 300 miscarriages each year that are caused by the process, known as CVS,” explained Collins.
“At £400 [approximately US $622] per test, it is currently too expensive to adopt across the country but researchers hope the pilot will persuade pharmaceutical bosses to drop the cost to a price the health service can afford,” he said, adding that it “could be many years before it becomes more widely available because no laboratory in the UK is capable of carrying out the analysis.”