Chicago – A study conducted by UCSF scientists show that a Roche blood test or cell-free DNA test delivers far accurate detection of Down syndrome in pre-natal tests as compared to standard tests. While the case sets the stage for a wider use of these Roche blood tests, experts have some reservations.
According to them, women need to confirm the results through taking more invasive diagnosis like amniocentesis, despite the accurate results, particularly if they are reviewing to terminate the pregnancy.
The new Roche harmony test screens the fetal genetic biomarkers in the mother’s blood while the standard screening test observes ultrasound and protein markers in the mother’s blood. Dr. Mary Norton of the University of California, San Francisco said that the test is great but since it doesn’t detect everything, therefore, it is not dependable to take final decisions.
Positive results returned from either Roche harmony test or standard test needs to be validated through amniocentesis. This invasive test collects a sample of amniotic fluid or a sample of the fetus’ placenta and carries a risk of miscarriage. Therefore, it is recommended only for women falling in the high-risk category.
The study evaluated 16,000 women, where the DNA test showed that 38 fetuses had Down Syndrome, out of which, only nine turned out to be false positives. The results produced are far more accurate than the standard screening test that showed that 854 false positives.
Dr. Arzou Ahsan, an obstetrician with East Bay Physician Medical Group, said that clearly the DNA test is superior and should help to lower down the amniocenteses going forward. However, Ahsan said that the utility of DNA test is limited to screening Down syndrome and a bunch of other chromosomal disorders. Hence, it is not appropriate to identify a more wide range of genetic irregularities.
Dr. Norton concluded that the newer test is more relevant to women of age 35 and over, who have higher chances of having a child with Down syndrome. While women under the age 35 could rely on standard blood screening.