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Application of non-invasive prenatal testing for the screening of fetal chromosomal abnormalities in 12 085 cases

To assess the value of non-invasive prenatal testing (NIPT) for the screening of fetal chromosomal abnormalities. For 12 085 pregnant women, the results of NIPT and invasive prenatal diagnosis were compared. The test was successful in 12 067 cases and has detected 179 chromosomal abnormalities, with a positive rate of 1.48%, sensitivity of 98.39% and specificity of 99.02%. Invasive prenatal diagnosis was performed for 3 of 18 patients who had failed NIPT but has detected no karyotypic abnormality. Except for one case of twin Cesarean section which delivered a normal female fetus and a stillbirth of unknown sex, the remainder of the 18 cases all had a normal delivery. The positive rate of NIPT screening for the abnormal ultrasound group was significant higher than that other groups (P< 0.01). Among those with positive results of NIPT, 122 underwent invasive prenatal diagnosis, and 25 trisomy 21, 7 trisomy 18, 3 trisomy 13, 4 aneuploidies of other autosomes, 13 sex chromosomal aneuploidies and 9 microdeletion/microduplications were confirmed, which yielded a positive predictive rate of 86.21%, 50.00%, 23.08%, 21.05%, 46.43%, and 47.36%, respectively. NIPT has high sensitivity, specificity and positive predictive value, and is an effective method for prenatal screening. In addition to chromosomes 21, 18 and 13, NIPT has certain predictive value for other autosomal aneuploidies, sex chromosomal aneuploidies, microdeletion/microduplications, and can provide a reference for karyotype analysis and chromosomal microarray verification.

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Retrospective analysis and mining of data from 10 840 patients undergoing non-invasive prenatal screening

To retrospectively analyze non-invasive prenatal screening (NIPS) data from two centers. The NIPS results of 10 840 samples were analyzed, including 21/18/13 trisomies (T21/T18/T13), sex chromosome and other autosomal aneuploidies, and copy number variants (CNVs). The maternal age, gestational week, body mass index and concentration of free fetal DNA (cffDNA) were also analyzed. The average gestational age of the 10 840 pregnant women was (32.34Âą5.04) year old, and the average gestational week for NIPS was (17.60Âą3.55) week. The overall false positive rate for T21/T18/T13 was 0.11%, sensitivity was 100%, specificity was 99.89%, and positive predictive value was 81.5%. The positive predictive values for sex chromosome and other autosomal aneuploidies and CNVs were 56.67%, 11.76% and 83.33%, respectively. The incidence of T21/T18 in the elder women (35 years or elder) was 2.12 times(P<0.01) and 1.81 times (P> 0.05) that of young women. cffDNA was in proportion to gestational week (r = 0.207) and in inverse proportion to body mass index (r = -0.177). It has increased slowly before 15 weeks of gestation and thereafter at a rate of 0.5% per week after the 16th week. The performance of NIPS in this study is by large close to the reported in the literature, and the results can provide a reference for further study.

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Phenotypic and genotypic analysis of a pedigree affected with hereditary protein C deficiency due to heterozygous deletional mutation of PROC gene

To analyze the phenotype and genetic variants of a pedigree affected with hereditary protein C (PC) deficiency. The protein C activity (PC:A) of the proband and her family members (a four-generation pedigree including 11 individuals) were tested by chromogenic substrate method, and the protein C antigen (PC:Ag) was detected with an enzyme-linked immunosorbent assay(ELISA). The 9 exons and flanking sequences of the protein C (PROC) gene were amplified by PCR and directly sequenced. Suspected mutation was validated by clone sequencing and in other members of the family. MutationTaster and ClustalX-2.1-win was used to analyze the pathogenicity and conservation of the mutation site,respectively. Three-dimentional protein model and amino acids interaction were analyzed with Swiss-PdbViewer software. The PC: A and PC: Ag of the proband were decreased to 46% (reference range: 70%-130%) and 50% (referencerange:70%-140%), respectively. Her grandmother,aunt, cousin and younger brother also showed declined PC:A and PC:Ag by approximately 50%. Genetic analysis revealed that the above individuals have all carried a deletional mutation c.1212-1212delG (p.Met364TrpfsX15) in exon 9 of the PROC gene which can cause replacement of Methionine at position 364 by Tryptophan and alteration of 15 downstream amino acids, and produce a premature stop codon at position 378. The score of MutationTaster was 1.000, indicating that the variant is pathogenic. Conservative analysis showed that the 15 altered amino acids are located in a conserved region across nine homologous species. Protein model analysis showed that the mutation has disrupted a catalytic domain of protein C thereby affected its function. The heterozygous c.1212-1212delG deletional mutation in exon 9 of the PROC gene, which was unreported previously,probably accounts for the decrease of PC:A and PC:Ag in this pedigree.

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