New test is "going to be a very big change for doctors and patients" ... Dr David Amor
A new safe, more accurate method of detecting Down syndrome is being used in Australia, dramatically decreasing anxiety among expectant parents.
The blood test is more accurate than current methods and reduces the need for risky invasive procedures that can trigger miscarriage.
Two new UK studies published in the journal Ultrasound in Obstetrics & Gynaecology suggest that the test, referred to as cfDNA, could be routinely offered in the first trimester.
David Amor, a clinical geneticist at the Murdoch Children’s Research Institute in Melbourne, said the test had been available in Australia for about three months.
Blood specimens are sent for testing to the United States at a cost of $850 to $1250, but Dr Amor expected the price to come down to about $650 by the end of 2013.
"It is going to be the way testing is done in the future ... It is going to be a very big change for doctors and patients," Dr Amor said.
"It is a far preferable test because it gives far more precise answers and takes away the uncertainty. It will lead to far fewer invasive tests being performed."
Dr Amor said he believed Australian test analysis is about a year away.
At present, most testing involves an ultrasound scan and a maternal blood test. Together, these give a risk estimate, and parents must then decide if they want to go ahead with the accurate but risky invasive tests amniocentesis and chorionic villus sampling (CVS). These both use a needle via the mother’s pregnant stomach, and carry a very small risk of miscarriage.
Dr Amor said the one weakness of the new test is that there is still a risk of false-positive results. Even though the false-positive rate is less than one per cent, he said amniocentesis and CVS, would still be necessary for some.
"The consequences of terminating a healthy pregnancy is obviously major, so it is recommended that women with abnormal non-invasive tests still have an amnio or CVS to confirm the results," he said.
"[But] what the new test will do is greatly reduce the number of amnios and CVSes that are done."
The UK studies, led by Kypros Nicolaides of London’s King’s College, are the first to show that the new tests are feasible for routine first-trimester screening.
Testing done in 1005 pregnancies at 10 weeks had a lower false-positive rate and higher sensitivity than the current testing method.
"Another major advantage of cfDNA testing is the reporting of results as very high or very low risk, which makes it easier for parents to decide in favour of or against invasive testing," the authors wrote.
- With AAP