Application Of CNV-seq Joint Chromosome Karyotype Analysis Under Different Prenatal Diagnostic Indications

Objective(s):Based on 431 cases of chromosomal abnormalities of fetal cells in the high-risk pregnant women of the amniotic fluid of chromosome copy number variation sequencing technology(Copy Number Variation sequencing,CNV-seq)and chromosome karyotype analysis,discusses the application of combination of both prenatal diagnosis technology in application value under different indications of prenatal diagnosis.Methods:A total of 431 singleton pregnant women with different prenatal diagnosis indications were selected from April 2020 to October 2022.All pregnant women underwent amniocentesis,and the amniotic fluid specimens were analyzed by CNV-seq and chromosome karyotype.The abnormal fetal staining was statistically analyzed by chromosome karyotype analysis alone,CNV-seq alone and the combined analysis of the two detection techniques,and the detection rate of abnormal chromosomes among the three detection methods was compared.Then,according to the classification of prenatal diagnostic indications,the combined application of the two detection techniques under different indications for fetal chromosome abnormalities was analyzed.Results:1.The success rate of CNV-seq and chromosome karyotype analysis in 431 amniotic fluid samples was 100%.2.The detection rate of fetal abnormal chromosomes by chromosome karyotype analysis alone was 30.16%(130/431);The detection rate of abnormal chromosome in the fetus using CNV-seq alone was 64.04%(276/431).The detection rate of abnormal chromosome by CNV-seq karyotype analysis was 73.55%(317/431).The detection rate of fetal abnormal chromosomes by CNV-seq combined chromosome karyotype analysis was significantly higher than that by chromosome karyotype analysis and CNV-seq alone,and the difference among the three detection methods was statistically significant(P<0.05).3.The comparison between CNV-seq and chromosome karyotype analysis showed that 30 cases of chromosome aneuploidy were detected in both cases,but 14 PCNVs were not detected by chromosome karyotype analysis.5 cases of inversion,1 case of translocation and 3 cases of homologous chimeras were not detected by CNV-seq.4.Among the pregnant women who visited the clinic for different prenatal diagnosis indications,the pregnant women who received prenatal diagnosis with abnormal ultrasound and mixed indications accounted for the largest proportion.There were significant differences in the detection rates of fetal abnormal chromosomes by chromosome karyotype analysis alone,CNV-seq alone and the combined analysis of the two detection methods under different indicators(P<0.05).There was significant difference between single chromosome karyotype analysis and combined analysis(P<0.05).There was no significant difference between CNV-seq alone and the two detection methods combined analysis(P>0.05).5.Under different prenatal diagnostic indications,the highest detection rate of fetal abnormal chromosomes by CNV-seq joint chromosome karyotype analysis was in pregnant women with mixed indications and ultrasound abnormalities,respectively:26.50%,25.87%,followed by NIPT or NIPT Plus abnormal pregnant women,14.51%,due to husband/wife chromosome abnormality pregnant women,the least,0.95%.6.The number of older pregnant women over 40 years old was higher than that between 35 and 39 years old,and there was statistical significance between the two ages(P<0.05).However,the detection rates of abnormal chromosomes in fetus between 35 and 39 years old and above 40 years old were 66.67%and 61.54%,respectively,and the difference was not statistically significant(P>0.05).7.The results of NIPT were verified by CNV-seq karyotype analysis,and the positive predictive value was 42.55%.The positive predictive value of trisomy 21 was the highest,accounting for 83.33%,followed by the abnormal prediction of the number of sex chromosomes,accounting for 52.17%.In addition to chromosome aneuploidy,NIPT can detect some CNVs.However,CNV-seq karyotype analysis did not detect trisomy 21 and trisomy 18 in pregnant women with abnormal Down’s screening,and the positive predictive value was 0.8.Among pregnant women with ultrasound abnormalities,the 5 cases of causative chromosome variation detected by CNV-seq joint chromosome karyotype analysis were indicated by ultrasound abnormalities including nasal bone loss in 2 cases,NT thickening(3.9mm)in 1 case,abnormal cardiovascular indicators in 1 case,and abnormal soft indicators in 2 or more cases in 1 case.9.Trisomy 21,XYY syndrome,homologous chimerism and PCNVs detected in pregnant women with mixed indications were all diagnosed prenatal at older age with other indications.Conclusion(s):1.Using CNV-seq combined karyotype analysis under different prenatal diagnostic indications can significantly improve the detection rate of fetal chromosome abnormalities,and can make up for the defects of chromosome karyotype analysis alone can not detect PCNVs and CNV-seq alone can not detect chromosome cross-translocation,inversion and other chromosome balance structure rearrangement and homologous chimeric defects.2.The number of cases over 40 years old was significantly higher than that of pregnant women between 35 and 39 years old,but in the older pregnant women,the increase of age did not significantly increase the detection rate of fetal chromosome abnormalities.3.The positive predictive value of NIPT or NIPT plus for trisomy 21 and trisomy 18 was significantly higher than that of Down’s screening.