The Application Value Of Noninvasive Prenatal Testing In The Detection Of Fetal Chromosomal Abnormalities In Ningxia

Objective To investigate the value of noninvasive prenatal testing for fetal sex chromosome abnormalities in Ningxia area’s.Methods cff-DNAs were collected from 7619 cases of single pregnant women(12~26weeks pregnant)in NingXia area’s prenatal diagnosis center who are voluntarily receiving noninvasive prenatal from 2014 to 2017.Amniotic fluid puncture and fetal karyotype analysis were carried out for fetal sex chromosome abnormalities of fetus on the test results.Acquisition of fetal chromosomal karyotype by amniocentesis as gold standard.NIPT by high-throughput sequencing technology were used to find out the sex chromosome abnormalities of fetus with false positive result need to withdrawn a maternal blood sample(5ml)producer,and then obtaining the karyotype of mother’s chromosome.After delivery,take the placenta tissues near the fetal surface of placentaor,then DNA sequencing.Or withdrawn of 5ml from the peripheral blood of newborns to obtain chromosomal karyotype.All the pregnant women who had noninvasive prenatal examination were followed up.Results The study enrolled 7619 pregnant women who were prepared to undergo NIPT.Of these,32 pregnant women(0.42%)showed fetal sex chromosome abnormalities,including19 with less number of sex chromosomes and 13 with more number of sex chromosomes.Thirty-two pregnant women agreed to undergo fetal karyotyping and 18 had results consistent with NIPT,while 14 patients received a normal karyotype result.The overall positive predictive value of NIPT for detecting sex chromosome abnormalities was56.2%(18/32).The specificity,sensitivity,and negative predictive value of noninvasive prenatal detection for fetal chromosomal abnormalities were 99.8%,100%,and 100%,respectively.Karyotype confirmed that 18 cases of sex chromosomal abnormalities including7 cases of 45,X(including 3 cases of chimeric type),4 cases of 47,XXX(1 cases of chimeric type),5 cases 47,XXY,2 cases 47,XYY and 14 cases 46,XN.The positive predictive value of non invasive prenatal detection was 36.8%(7/19)for those with less sex chromosomes,and for those more sex chromosomes was 84.6%(11/13).Among them,47,XXX,47,XXY,and 47,XYY accounted for 30.8%,38.5% and 15.4% of the total number of sex chromosomes.Noninvasive prenatal measurement of fetal chromosome abnormalities in14 cases of false-positive postpartum placental specimens karyotype analysis/neonatal peripheral blood and maternal peripheral karyotype analysis results suggest that 4 cases of placental mosaic(28.6%),4 cases of mothers Chromosome abnormalities(28.6%),relatively low free DNA content in the peripheral blood of 2 mothers(14.3%),1 potential tumour in the mother(7.1%),and normal chromosomes in 3 mothers and fetuses(21.4%),Eliminate other factors and consider the accuracy set for computer verification programs.Conclusion Based on the current sample size in the region,this study draws the following conclusions:1.In NingXia area,noninvasive prenatal detection technology can be used for the detection of fetal sex chromosome abnormalities,but its false positive rate is relatively high,and the positive predictive value of noninvasive prenatal detection technology is higher for those with more number of sex chromosomes.2.Noninvasive prenatal detection techniques occur fetal chromosome abnormalities false positive results for NingXia region,the main reason is due to placenta mosaicism and maternal chromosome abnormalities.3.In the detection of targeted chromosomal abnormalities,NIPT technology has further room for improvement in the optimization of algorithms and the accuracy of calculations.