Washington, October 7 : Scientists in the U.S. have developed a new prenatal blood test that can accurately detected Down syndrome and two other serious chromosomal defects.
Howard Hughes Medical Institute researchers say that they have already tested the new test on a small study sample of 18 pregnant women.
The researchers believe that the test can offer a safer and faster alternative to invasive prenatal tests such as amniocentesis, which pose a small risk of miscarriage.
They point out that a pregnant woman's blood contains small amounts of DNA from the foetus, and their test offers an ingenious way to scan the foetal DNA to determine whether the foetus' cells contain extra chromosomes linked with several types of severe birth detects.
Project leader Stephen R. Quake, a bioengineer at Stanford, said that the new test was more accurate than techniques used in previous efforts to diagnose aneuploidy by analysing foetal DNA.
Aneuploidy occurs when there are either too many or too few chromosomes in cells. Down syndrome, for example, is caused by a trisomy -- three copies instead of two -- of chromosome 21.
"We believe this is the first demonstration of a universal, non-invasive test for Down and other aneuploidies. We need a larger clinical study to understand a bit more about the best way to implement it, but I am highly optimistic it will be used as a diagnostic test in short order," said Quake.
With the new test, scientists only need to draw a small amount of blood from the woman for its analysis, and the results are available within a couple of days, said Quake.
The research also insists that the new approach can help detect higher-than normal amounts of DNA belonging to the three chromosomes involved in the most common aneuploidies -- chromosomes 21, 18, and 13.
Quake said that during the tests on 18 pregnant women, he and his colleagues were able to correctly identify the 12 women who carried aneuploid foetuses, and the six whose pregnancies were normal.
He said that the new approach was not only safer than invasive techniques, but could also make a determination at an earlier gestational age, around 12 weeks.
He is now planning a follow-up study to evaluate the test in a larger group of patients.
The research has been published in the online edition of the Proceedings of the National Academy of Sciences (PNAS).