First study to show high accuracy of non-invasive prenatal testing in average-risk pregnant women
San Jose, Calif., Sept. 5, 2012 – A study just published in the American Journal of Obstetrics and Gynecology (The Gray Journal) provides substantial new evidence that the Harmony Prenatal Test, a specific type of non-invasive prenatal test (NIPT), is effective in a general screening population. In this study, the test detected all cases of fetal trisomy 21 and 18 at a false-positive rate of 0.1 percent.
The study, “Noninvasive Prenatal Testing for Fetal Trisomies in a Routinely Screened First-Trimester Population,” was led by Dr. Kypros H. Nicolaides, professor at the Harris Birthright Research Centre for Fetal Medicine at King’s College Hospital in London, with fellow authors Argyro Syngelaki, Dr. Ghalia Ashoor, Dr. Cahit Birdir and Dr. Gisele Touzet.
The Harmony test is a type of NIPT utilizing a directed approach to cell-free DNA (cfDNA) analysis and provides an individualized risk assessment for trisomy (the presence of three chromosomes instead of two). It involves a single blood draw taken as early as 10 weeks’ gestation and delivers a greater than 99 percent detection rate for trisomy 21, which causes Down syndrome. Much of the research on NIPT to date has focused on women determined to be at a high-risk for trisomy.
“This excellent study validates the detection of fetal trisomy through analysis of maternal plasma using chromosome-selective, cell-free fetal DNA sequencing in an average-risk population. False positive diagnoses were rare (2 per 1949), but the few encountered indicate that invasive procedures are still necessary on occasion for confirmation,” said Dr. Joe Leigh Simpson, senior vice president for Research and Global Programs at the March of Dimes. He added, “False positive results could be due either to confined placental mosaicism or to unrecognized demise of an aneuploidy co-twin. Overall, it is clear that cell-free fetal DNA analysis is becoming the preferable method for fetal aneuploidy screening.”
The cohort study evaluated 2,049 pregnant women undergoing routine screening for fetal trisomy in the first trimester using Ariosa Diagnostics’ Harmony Prenatal Test. Results of the blinded study are provided as a risk score (percent) for trisomy 21 and trisomy 18. The trisomy risk score was greater than 99 percent in all the trisomy cases (eight cases of trisomy 21 and two cases of trisomy 18). The false positive rate was 0.1 percent for trisomy 21 and trisomy 18 using the Harmony test as compared to a 4.5 percent false positive rate with traditional combined first trimester screening with serum markers and nuchal translucency measurement. The results from this study contribute to the more than 200 trisomy 21 cases and 100 trisomy 18 cases now detected with Ariosa’s directed cfDNA method. Full details of the general screening population study are available online at: http://www.ajog.org/webfiles/images/journals/ymob/AJOG_Nicolaides.pdf and will be published in print in the upcoming months.
The study builds on other recent findings that support the utility of NIPT for any pregnant woman, regardless of risk categorization. Other studies have shown no significant differences in the fraction of fetal cfDNA in blood in women 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.
“This study affirms our commitment to leading the introduction of NIPT into medical practice based on robust clinical data. We have now studied over 6,000 women including 2,000 low risk women across multiple studies,”said Ariosa Diagnostics CEO Ken Song, MD. “The Harmony Prenatal Test represents a major advance in obstetrics that can provide highly accurate information to women so as to better manage their pregnancy.”