Clinical Study of Non-Invasive Prenatal Testing Using Next-Generation Sequencing

BACKGROUND: Serological prenatal screening tests are widely used to detect fetal chromosomal abnormalities such as Down and Edward syndromes. After determining the presence of fetal cell-free DNA in maternal blood, the non-invasive prenatal test (NIPT) coupled with next-generation sequencing has been performed in other countries, therefore, we developed a domestic NIPT technology. METHODS: The results of genomics-based NIPT performed between April and May, 2015 were analyzed. Maternal blood samples were collected in a specific Cell-Free DNA BCT tube. The samples were then massively sequenced using MiSeq and NextSeq 500 (Illumina Inc., USA) using LabGenomics laboratory-developed libraries. Chromosomal abnormalities were analyzed using a bioinfomatics algorithm. RESULTS: A total of 464 cases were analyzed. The samples of 12 subjects had to be collected again because of a low fetal DNA fraction in the initially obtained samples. Among the 456 cases for which fetal genome results were obtained, 436 had a low risk of trisomy, 12 had a high risk for Down syndrome, two had a high risk for Edward syndrome, and four had sex chromosomal aneuploidy, showing that the positive percentage of chromosomal abnormalities was 4.4%. All 12 cases with high risk for Down syndrome were confirmed as having trisomy 21 by amniocentesis. CONCLUSIONS: Our laboratory-developed genomics-based NIPT showed high positive predictive value, therefore, NIPT may be replaced by our own developed method.

An Experience of Using the Harmony Test for Genomics-Based Non-Invasive Prenatal Testing / 임상검사와정도관리

Serological prenatal screening tests are widely used to detect fetal chromosomal abnormalities such as Down and Edward syndromes. Amniocentesis is conducted as a confirmatory test in the screening-positive case. After discovering of presence of fetal cell-free DNA in maternal blood, non-invasive prenatal test (NIPT) coupled with next generation sequencing are performed in abroad. Results of genomics-based NIPT results supplied to Labgenomics laborotory from June, 2013 to August, 2014 were analyzed. Maternal blood samples were collected into specific Cell-Free DNA BCT tube and were transported. The samples were then delivered to Ariosa Diagnostics by FEDEX. Fetal cell-free DNA samples were analyzed using the Harmony test with sequencing of relevant chromosomes and by using the FORTE (fetal-fraction optimized risk of trisomy evaluation) algorism at Ariosa Diagnostics. In all, 149 cases from 28 medical clinics were analyzed. Six subjects were required recollection of samples because of a low fetal DNA fraction in the initially obtained samples. Of these 6 subjects, no sample could be collected from one. Of the remaining 148 cases, 144 had a low risk of trisomy, and 4 had a high risk for Down syndrome, thus providing a positivity percentage of 2.7%. Fetal DNA fraction in the maternal blood samples ranged from 4.2% to 23.7% with a mean value of 12.0%. We have experienced cases with a high risk for Down syndrome with genomics-based NIPT referred to abroad.