Philippos Patsalis, PhD, HCLD, head of the research team at The Cyprus Institute of Neurology & Genetics, announced earlier this week that he and his team have developed and validated a noninvasive prenatal test for Down Syndrome (Trisomy 21). The maternal DNA blood test is considered to be a significant improvement over current testing methods. These include amniocentesis and chorionic villi sampling, both invasive techniques.
The new, noninvasive test developed by Patsalis and his team uses a small amount of blood from the pregnant woman. Their study involved the collection of 10 ml of blood, at 11 to 14 weeks of gestation, from 80 pregnant women. Of these 80 blood samples, 34 were from pregnancies carrying a fetus with Down Syndrome, and 46 were from pregnancies carrying a fetus with normal constitution.
All normal and all Down Syndrome cases were correctly identified, providing 100% specificity and 100% sensitivity. The development and validation of the novel method was published online in Nature Medicine last week.
Patsalis reports that the success of the test is based on the investigation of epigenetic markers on chromosome 21 that are located exclusively in the fetal DNA. In cases where the fetus has Down Syndrome, there will be an extra copy of the fetal-specific epigenetic marker together with the extra chromosome 21. The test is able to quantify this extra copy of chromosome 21 and distinguish normal pregnancies from pregnancies bearing a Down-syndrome fetus.
The Cyprus Institute of Neurology and Genetics expects its new test to be introduced with high confidence as a routine test in clinical practice in the near future, perhaps as soon as two years from now. It lists the advantages of the test as follows: 1. The noninvasive test carries no risks for fetal loss; 2. The test can be offered to all pregnant women; and 3. It can provide effective prevention of Down Syndrome. Additionally, the Institute says the test provides 100% accuracy in the prenatal diagnosis of Down Syndrome, and the application of the test is relatively simple and does not require specialized or complex laboratory equipment, software, infrastructure, or knowledge.
The cost of performing this test is less expensive than the current methods used for invasive prenatal diagnosis, the Institute says. And it yields results quickly, in 4-5 days.
Patsalis and his team are now in the process of performing a larger-scale clinical study, which is essential to enabling the introduction of the new test into clinical practice. The research team is also researching the modification of the new test so it can be utilized for the noninvasive prenatal diagnosis of other syndromes.
Down Syndrome or Trisomy 21 is the most common cause of mental retardation, with an incidence of 1 in 600 births. It is caused by the presence of an extra chromosome 21, which leads to physical and intellectual impairments.
---Maureen Kingsley, Associate Editor