| ObjectiveNoninvasive Prenatal Testing(NIPT)is considered as an earlier,safer,more rapid and more accurate detection method,due to its higher sensitivity and lower false positive rate.This study mainly explores the application of NIPT by analyzing the data from 2014 to 2017 in the Obstetrics of Jiangmen Central Hospital.Methods1,A total of 20,670 pregnant women with NIPT were collected at the Obstetrics of Jiangmen Central Hospital from 2014 to 2017.All patients signed the Informed consent for Noninvasive Prenatal Testing(NIPT).Among them,19908 were single pregnancy at the age of 31.08±5.14 and the gestational age of 15.86±3.93,and 762 were twin pregnancies at the age of 30.63±4.18 and the gestational age of 14.89±3.06.2,Blood Sample collection: 5 ml of peripheral venous blood of pregnant women was extracted and put into the EDTA anticoagulant tube.Plasma was obtained by two-step separation within 8 hours and stored in a refrigerator that was-80?.3.Laboratory procedures: 1)DNA extraction and segmentation: plasma separation-> DNA extraction-> DNA fragment end repair;2)DNA fragment amplification(nanosphere technology): add the splice sequence-> PCR amplification->pooling library-single strand preparation of >DNA and ring-ring amplification-> DNB rolling ring amplification-> to form DNA nanospheres;3)DNA sequence recognition: DNA nanosphere attached chip-> combined probe anchored connection sequencing;4)analysis: base-reading-> data comparison and assembly-> chromosome triploid analysis-> result review;4.T value and L value are used to determine the risk of chromosome aneuploidy(mainly including trisomy 21,trisomy 18 and trisomy 13).Invasive prenatal diagnosis should be used to make a definite diagnosis for the high-risk cases.Results1 Single pregnancy1.1 NIPT indicated that a total of 108 cases were at high risk of T21/T18/T13,and 93 cases were consistent with the results of prenatal diagnosis or postpartum karyotype analysis,The positive predictive value(PPV)was 86.11%,the false positive rate(FPR)was 0.07%,and the sensitivity was 100%.The PPV of T21/T18/T13 was 94.81%,82.35%,50%,respectively.The FPR of T21/T18/T13 was 0.02%,0.02%,0.04% respectively.The sensitivity were 100%.1.2 The PPV of NIPT in screening for sex chromosome abnormalities was 56.92%,the FPR was 0.14% and the sensitivity was 100%.1.3 The PPV of NIPT in screening for CNVs was 33.33%,the FPR was 0.17% and the sensitivity was 100%.2 Twin pregnanciesThe PPV of NIPT for screening chromosome aneuploidy in twin pregnancies was 75%,the FPR was 0.26% and the sensitivity was 100%.3.There was no significant difference between single pregnancy and twin pregnancies in maternal age and gestational age.In the screening for T21/T18/T13,the PPV of twin pregnancies was lower than that of single pregnancy,and the FPR was higher than that of single pregnancy,but there was no significant difference between them.Conclusions1.As a prenatal detection method,compared with serological screening,NIPT has a significantly higher PPV and a lower FPR,which is conducive to reduce the proportion of invasive prenatal diagnosis.2.NIPT has certain false positive and false negative.Therefore,it can only be used as a detection method for fetal chromosome aneuploidy,but not a diagnosis method.3.Benefiting from the development of NGS,NIPT was not only used to detect T21/T18/T13,but also to achieve satisfactory results for the detection of abnormal sex chromosome number(especially increased sex chromosome number)and CNVs.4.The accuracy of NIPT in twin pregnancies is similar to that of single pregnancy.NIPT can be recommended as the first choice for prenatal screening of twin pregnancies.5.It is necessary to pay attention to the limitations of NIPT in the clinical application. |
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