e1-5.). Reprints are available from Hong Jiang, MD, Reproductive Medicine Centre, 105 Hospital of PLA, 424 Changjiang Rd, Hefei, China. [email protected]. “
“The recent introduction of cell-free DNA (cfDNA)-based noninvasive prenatal testing (NIPT) has offered pregnant women a more accurate selleck method for detecting fetal aneuploidies than traditional serum screening methods.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 NIPT noninvasively determines fetal chromosome copy number by interrogating
cfDNA isolated from maternal plasma, with the fetus contributing anywhere from <2% to >30% of the total cfDNA.3, 7 and 13 Other NIPT approaches use quantitative “counting” methods where fetal chromosome copy number is determined by comparing click here the absolute number of sequence reads from the chromosome(s) of interest (eg, chromosome 21) to reference
chromosome(s), and inferring fetal trisomy when this ratio is above a predetermined threshold. This approach cannot determine the source of DNA (fetal or maternal) and is therefore unable to detect additional fetal haplotypes associated with triploidy or vanishing twins. Vanishing twins were reported to account for 15% of false positives in a recent counting-based NIPT study.14 This likely results in unnecessary invasive prenatal testing. A more recent approach using a single-nucleotide polymorphism (SNP)-based method along with sophisticated informatics can resolve this potential source of false-positive results. This approach identifies the presence of additional fetal haplotypes, indicative of a triploid or dizygotic multifetal pregnancy, and determines parental origin.10 and 12 Using the SNP-based approach, the prevalence of cases found to have additional fetal haplotypes
within 30,795 consecutive cases undergoing routine clinical NIPT was determined, and is reported here. Clinical follow-up of these cases is also described. The current study included all samples from participating centers received for commercial testing from March 1, through Nov. 30, 2013, that received an NIPT result. This study received a notification of exempt determination from an institutional review board (Ethical and Independent Review Services, Oxalosuccinic acid no. 14064-01). All samples were analyzed at Natera’s Clinical Laboratory Improvement Act–certified and College of American Pathologists–accredited laboratory in San Carlos, CA. Analysis was performed for all samples on chromosomes 13, 18, 21, X, and Y, and included detection of trisomy 21, trisomy 18, trisomy 13, monosomy X, sex chromosome abnormalities (47,XXX/XXY/XYY), fetal sex, and additional fetal haplotypes. Maternal blood samples (>13 mL) were collected in Streck (Omaha, NE) blood collection tubes and processed at Natera (San Carlos, CA) within 6 days of collection.
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