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Will cell-free DNA testing replace amniocentesis?
An analysis conducted at 21 US centers suggests that maternal plasma cell-free DNA (cfDNA) testing should be considered as primary screening for fetal autosomal aneuploidy. The findings, from the Comparison of Aneuploidy Risk Evaluation (CARE) Study Group, were presented at the 18th International Conference on Prenatal Diagnosis and Therapy and published in Prenatal Diagnosis.
Blood samples were drawn at 8 weeks’ gestation from 1914 women (mean age 29.6 years) pregnant with singletons who were undergoing serum biochemical assays with or without nuchal translucency measurement. The investigators performed massively parallel sequencing in blinded fashion to determine the chromosomal dosage of each sample and to compare false-positive rates for cfDNA sequencing with those for standard aneuploidy screening.
With cfDNA testing, significantly lower false-positive rates were seen for trisomies 21 and 18. A trend toward significant improvement in false-positive rate for trisomy 13 was seen in 899 patients with risk classification by standard screening.
All cases of aneuploidy (5 trisomy 21, 2 trisomy 18, 1 trisomy 13) were detected by cfDNA testing. The screening had positive predictive values of 45.5% for trisomy 21 and 40% for trisomy 18 versus 4.2% and 8.3%, respectively, for standard screening.
The authors noted that the results represented an improvement by a factor of 10 in the positive predictive value for trisomy 21 in a predominantly low-risk patient population, suggesting that “cfDNA testing merits serious consideration as a primary screening method for fetal autosomal aneuploidy.”
Sehnert A, Bianchi D, Rava R, CARE Study Group. Maternal cell-free DNA (cfDNA) sequencing versus standard prenatal aneuploidy screening in a general obstetrical population. Prenat Diagn. 2014;34(Suppl. 1):8. Abstract 6-1.