Validation of targeted sequencing of single-nucleotide polymorphisms for non-invasive prenatal detection of aneuploidy of chromosomes 13, 18, 21, X, and Y.

OBJECTIVE: To assess the performance of cell-free DNA (cfDNA) testing in maternal blood for detection of fetal aneuploidy of chromosomes 13, 18, 21, X, and Y using targeted sequencing of single-nucleotide polymorphisms.

METHODS: Prospective study in 242 singleton pregnancies undergoing chorionic villus sampling at 11 to 13 weeks. Maternal blood was collected before chorionic villus sampling and sent to Natera (San Carlos, CA, USA). cfDNA was isolated from maternal plasma, and targeted multiplex PCR amplification followed by sequencing of 19 488 polymorphic loci covering chromosomes 13, 18, 21, X, and Y was performed. Sequencing data were analyzed using the NATUS algorithm that determines the copy number and calculates a sample-specific accuracy for each of the five chromosomes tested. Laboratory personnel were blinded to fetal karyotype.

RESULTS: Results were provided for 229 (94.6%) of the 242 cases. Thirty-two cases were correctly identified as aneuploid, including trisomy 21 [n = 25; sensitivity = 100% (CI: 86.3-100%), specificity = 100% (CI: 98.2-100%)], trisomy 18 (n = 3), trisomy 13 (n = 1), Turner syndrome (n = 2), and triploidy (n = 1), with no false positive or false negative results. Median accuracy was 99.9% (range: 96.0-100%).

CONCLUSIONS: cfDNA testing in maternal blood using targeted sequencing of polymorphic loci at chromosomes 13, 18, 21, X, and Y holds promise for accurate detection of fetal autosomal trisomies, sex chromosome aneuploidies, and triploidy.