ABSTRACT
OBJECTIVE To analyze the data of non-invasive prenatal testing based on specific loci of circulating cell-free fetal DNA (cffDNA). METHODS Selected loci of target chromosomes were analyzed by sequence capture and sequencing. Meanwhile, 600 loci were selected from other chromosomes for determining the concentration of cffDNA. RESULTS A total of 768 specific loci were captured on chromosomes 21 and 18, and used to determine whether the two were abnormal. When the minimum concentration of detected cffDNA was set at 3% and the threshold of Z score was set to [-6,6], the specificity of the analysis was 99.37% and the sensitivity was 100%. CONCLUSION A reliable, convenient and low-cost analytical method has been developed. The method requires less sequencing data for non-invasive prenatal testing, and can accurately detect abnormalities of fetal chromosomes 21 and 18, and simultaneously determine the concentration of cffDNA.
ABSTRACT
Objective To establish a noninvasive prenatal testing(NIPT) method based on the chromosome specific site sequencing instead of the conventional whole genome sequencing.Methods Blood plasma samples from 200 pregnant women with known fetus karyotypes were collected.First,the specific loci on chromosome 13,18 and 21 were selected by the database filter.Then,these specific loci were captured by probes,and were performed sequencing.Finally,chromosome aneuploidy was identified by the Z-score.ResultsSeven fetuses with 21-trisomy syndrome,3 with 18-trisomy syndrome and 1 with 13-trisomy syndrome were detected by the chromosome specific site sequencing,and the results were accordant with those of the whole genome sequencing method.Conclusion The NIPT method based on the chromosome specific site sequencing has the advantages of low cost and high throughput,which may replace the NIPT method based on the whole genome sequencing.