Fetal fraction of cfDNA does not vary significantly among pregnant women regardless of trisomy risk

Published on August 28, 2012 at 4:16 AM · No Comments
A study published in The Journal of Maternal-Fetal and Neonatal Medicine demonstrates that the fraction of fetal cell-free DNA (cfDNA) in maternal blood is unaffected by the mother's presumed risk for trisomy, offering support for the use of non-invasive prenatal testing (NIPT) for detecting genetic conditions such as Down syndrome in a broad patient population. Lead and senior authors of the study were Dr. Herb Brar, Director of Riverside Perinatal Diagnostics Center, and Dr. Mary Norton, Professor of Obstetrics and Gynecology, Lucile Packard Children's Hospital at Stanford University, respectively.

Results of the study, a post-hoc comparative analysis of the previously published "Non-invasive Chromosomal Evaluation" (NICE) study, showed that there were no significant differences in the fraction of fetal cfDNA in maternal blood in women who were stratified into three different trisomy risk groups based on maternal age, prenatal screening results or nuchal translucency measurement. The amount of fetal cfDNA in maternal blood is the principal factor in successfully detecting trisomies with NIPT. Trisomy refers to the presence of three chromosomes rather than two. Certain trisomies are known to cause genetic conditions. The study is available at: http://informahealthcare.com/doi/abs/10.3109%2F14767058.2012.722731

"The results of this study were particularly significant because they showed that fetal fraction of cfDNA does not vary significantly among pregnant women regardless of their predetermined trisomy risk," said Dr. Herb Brar. "This adds to the growing amount of research that suggests NIPT can offer an effective prenatal screening option in the general pregnant population."

NIPT is a new screening option that analyzes cell-free fetal DNA circulating in maternal blood to evaluate the risk of having a baby with Down syndrome and other common genetic conditions. It involves a single blood draw as early as 10 weeks' gestation and delivers a greater than 99 percent detection rate for trisomy 21, which causes Down syndrome. NIPT, using the Harmony™ Prenatal Test, also has shown to have fewer false positive test results; up to 50 times less than traditional prenatal screening options such as maternal serum screening.

Previous studies of the entire cohort of the NICE study demonstrated that fetal fraction did not vary with race, ethnicity, maternal age, or trisomy type. It also showed that the fraction of fetal cfDNA was similar in pregnancies of gestational ages between 10 and 22 weeks. The NICE study was a prospective cohort study of more than 4,000 pregnant women of at least 10 weeks' gestational age across 50 clinical sites internationally. The study evaluated the performance of Ariosa Diagnostics' Harmony Prenatal Test in detecting fetal trisomy 21 and 18, which cause Down syndrome and Edwards syndrome, respectively.  The NICE study evaluated any patient undergoing invasive prenatal testing, such as chorionic villus sampling (CVS) or amniocentesis, not just those who were determined to be at higher risk of having a baby with a genetic condition.

"We believe strongly that scientific research supports NIPT as a screening option for any pregnant woman, empowering them and their physicians to make the best decisions for individual circumstances. This is simply good patient care," said Ariosa Diagnostics CEO Ken Song, M.D. "NIPT has proven effective in thousands of patients, with a high accuracy and low false positive rate of less than 0.1% for each trisomy tested. It offers several advantages over traditional screening tests and can more appropriately triage those women who should undergo invasive procedures, namely amniocentesis and CVS, which carry a small risk of miscarriage."

Source:

Ariosa Diagnostics, Inc.

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