A new study has found the new Roche blood tests very effective in screening fetuses for the proper determination of the Down syndrome.
According to researchers, the new testing methods were found to be largely ahead of the standard tests meant for the parental screening in younger women with low risk of developing the disease.
Even though the tests are path breaking, the experts caution women, who test positive in the screening, to consider additional invasive diagnostic tests like amniocentesis in order to confirm the results. The warning is particularly for those women who are considering termination of their pregnancy.
Dr. Mary Norton, of the University of California, San Francisco, said, “This is a great test for detecting Down syndrome but it doesn’t detect everything, it isn’t diagnostic, and it doesn’t always work to provide a result.”
Previous studies have shown that such fetal DNA tests measuring DNA fragments from the placenta circulating in the blood of mother are very accurate at detection of the Down syndrome and two other chromosomal abnormalities in high risk women, mainly those aged over 35.
For the study, Norton and his colleagues tested around 16,000 women with an average age of 30. Roche’s Harmony test was then compared with the standard parental screening for the Down syndrome relying on fetal ultrasound and biomarkers present in the blood via tests among women in the same group.
In comparison to the 30 cases of Down syndrome that were identified by the standard screening, the Roche test successfully detected 38 cases. The rate of false positive was 0.06 percent of the research work as compared with 5.4 percent for the standard screening.
But the cell free fetal DNA tests had nine false positive results in the group.
In addition, nearly 500 women the fetal DNA test failed to deliver any fruitful result in the absence of sufficient fetal DNA in the blood of the women. Further probe showed that nearly 2.7 percent fetuses witnessed chromosomal defects including instances that could not have been detected even the new fetal DNA technique.
The newer tests have not yet received approval from the FDA. Meanwhile, critics opine that companies are promoting the tests in a way that can be misleading for the patients.
The findings of the study were published in New England Journal of Medicine.