Researchers have found that a blood test carried out between 10 and 14 weeks of pregnancy is more effective in detecting Down syndrome as well as two other chromosomal abnormalities compared to non-invasive screening procedures.
In a study published in the New England Journal of Medicine, researchers detailed how a cell-free DNA blood test was able to correctly identify fetuses with Down syndrome, a condition associated with impairment in cognitive ability and higher risks for other medical disorders, offering results that were confirmed through newborn exams and prenatal or postnatal gene analysis.
Researchers followed nearly 16,000 women and their pregnancy outcomes, using fetal DNA found in pregnant women's blood to determine the presence of Down syndrome and other less common abnormalities. Cell-free DNA blood tests identified 38 fetuses with Down syndrome while standard screening only spotted 30 cases. An ultrasound to detect levels of nuchal fold fluid in the back of the neck was also done to complete the blood test screening because excessive amounts of fluid can hint at Down syndrome.
But while the cell-free DNA blood test has been found to be more superior than standard tests in detecting Down syndrome, Edwards syndrome and Patau syndrome, researchers cautioned that it is not able to identify risks in a wider range of abnormalities. Down syndrome, after all, accounts for just about 50 percent of aneuploidies or disorders resulting from the abnormal number of chromosomes.
Down syndrome is caused by an extra copy of chromosome 21 while Edwards syndrome is the result of three instances of chromosome 18. Patau syndrome, on the other hand, is due to the presence of three chromosome 13s.
Researchers pointed out the cell-free DNA blood tests will translate to fewer false positives and can reduce the need for invasive tests (consequently cutting the number of miscarriages they cause), but patients need to be made aware of the test's limitations.
Mary Norton, gynecology and clinical obstetrics professor from the University of California, San Francisco and first author for the study, said that healthcare providers need to know patient preferences so they can be counseled about different diagnostic testing and prenatal screening options.
"Counseling should also include information about the risks associated with failed tests and the pros and cons of pursuing invasive testing if no results are obtained," she added.
The study received funding support from the Perinatal Quality Foundation and Ariosa Diagnostics. Other authors who contributed to the study include: Ronald Wapner, Thomas Musci, Howard Cuckle, Desiree Hollemon, Jean Spitz, Leonardo Pereira, Mark Tomlinson, Herb Brar, Angela Ranzini, Louise Laurent, Geeta Swamy and Bo Jacobsson.
Photo: Bridget Coila | Flickr
