Researchers in Cyprus, Greece and Britain have identified and successfully tested a new noninvasive technique to detect Down syndrome in the fetuses of pregnant women. The results, published in Nature Medicine, indicate that a blood test for Down syndrome could be developed for women earlier in their pregnancies than is now possible.
Those with Down syndrome have three copies of Chromosome 21 instead of the normal two. It occurs in one out of every 700 births worldwide and women over the age of 40 are 16 times more likely to have a Down syndrome child than women at age 25. Right now, prenatal genetic diagnosis of Down syndrome--or trisomy 21--is performed using conventional cytogenetic or DNA analyses. That requires fetal genetic material to be obtained by invasive procedures such as amniocentesis, and carry with them a risk of fetal loss.
The new technique, very broadly, involves a comparison of what is known as free fetal DNA (ffDNA) found in the mother's blood and the mother's own DNA. The difference between the two has led to identification of what is known as differentially methylated regions (DMRs). The new study achieved noninvasive prenatal detection of Down syndrome through a comparison of the mother's DNA versus the fetus's. They were able to correctly diagnose 14 cases of Down syndrome and 26 normal cases.
"The method is simple and fast and easy to perform in every genetic diagnostic lab worldwide because it does not require expensive equipment, software or special infrastructure," said study author Philippos Patsalis, of the Cyprus Institute of Neurology and Genetics, as quoted in the London Daily Mail. "The test is the first worldwide to demonstrate 100 percent sensitivity and 100 percent specificity in all normal and Down syndrome pregnancies examined."
The researchers said a larger study is needed to confirm how useful the technique is, according to the Daily Mail.