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Cell-free DNA Analysis for Non invasive Examination of Trisomy
Mary E. Norton New England Journal Medicine Abril 2015
Background
Cell-free DNA (cfDNA) testing for
fetal trisomy is highly effective among high-risk women. However, there have
been few direct, well-powered studies comparing cfDNA testing with standard
screening during the first trimester in routine prenatal populations.
Methods
In this prospective, multicenter, blinded study conducted at 35 international centers, we assigned pregnant women presenting for aneuploidy screening at 10 to 14 weeks of gestation to undergo both standard screening (with measurement of nuchal translucency and biochemical analytes) and cfDNA testing. Participants received the results of standard screening; the results of cfDNA testing were blinded.
Determination of the birth outcome was based on diagnostic genetic testing or newborn examination. The primary outcome was the area under the receiver-operatingcharacteristic curve (AUC) for trisomy 21 (Down’s syndrome) with cfDNA testing versus standard screening. We also evaluated cfDNA testing and standard screening to assess the risk of trisomies 18 and 13.
Results
Of 18,955 women who were enrolled, results from 15,841 were available for analysis. The mean maternal age was 30.7 years, and the mean gestational age at testing was 12.5 weeks. The AUC for trisomy 21 was 0.999 for cfDNA testing and 0.958 for standard screening (P = 0.001). Trisomy 21 was detected in 38 of 38 women (100%; 95% confidence interval [CI], 90.7 to 100) in the cfDNA- testing group, as compared with 30 of 38 women (78.9%; 95% CI, 62.7 to 90.4) in the standard-screening group (P = 0.008). False positive rates were 0.06% (95% CI, 0.03 to 0.11) in the cfDNA group and 5.4% (95% CI, 5.1 to 5.8) in the standard-screening group (P<0.001). The positive predictive value for cfDNA testing was 80.9% (95% CI, 66.7 to 90.9), as compared with 3.4% (95% CI, 2.3 to 4.8) for standard screening (P<0.001).
Conclusions
In this large, routine prenatal-screening population, cfDNA testing for trisomy
21 had higher sensitivity, a lower false positive rate, and higher positive
predictive value than did standard screening with the measurement of nuchal
translucency and biochemical analytes. (Funded by Ariosa Diagnostics and
Perinatal Quality Foundation; NEXT ClinicalTrials.gov number, NCT01511458.)