基于高通量测序的孕妇外周血胎儿游离DNA产前检测的失败率及原因分析

Analysis to the failure rate and causes of noninvasive prenatal testing based on high-throughput sequencing

目的 对孕妇外周血胎儿游离DNA(cell-free fetal DNA,cffDNA)无创产前检测的失败原因及妊娠结局进行分析,探讨检测失败病例的处理方案。方法 对5898例妊娠12~22周的单胎孕妇进行外周血cffDNA检测,设定严格的质控标准,首次检测不达标者在知情同意后选择二次采血或直接进行产前诊断。结果 首次采血检测失败率为0.5%(32/5898),其中17例cffDNA%未达质控标准,10例两次建库检测均提示染色体数据波动,5例可能存在无法鉴别的性染色体异常。32例首次采血检测失败的病例中,2例直接接受了羊水细胞染色体核型分析,结果均未见异常;30例接受了重新采血,其中24例在二次采血后发放了检测报告,最终失败率为0.1%(8/5898)。二次采血共报告21三体、18三体、13三体高风险各1例,经羊水细胞染色体核型分析证实均为假阳性。6例二次采血检测失败病例中,1例产前诊断未见异常;1例产前诊断为mos45,X[32]/46,XY[18];4例未进行产前诊断,目前生长发育未见异常。结论 cffDNA比例低是检测失败的主要原因,但二次采血成功率较高,可有效增加最终检测成功率,减少侵入性检测数量,首次检测失败的孕妇在充分知情的前提下可考虑重新采血检测。

Objective To analyze the cause and pregnancy outcome for non-reportable cell-free DNA(cfDNA)results during non-invasive prenatal testing(NIPT).Methods cfDNA was extracted from maternal plasma from 5898 singleton pregnancies at 12 to 22 gestational weeks and underwent NIPT with strict quality control standards.For those with sub-standard results,redraw or invasive prenatal procedures were recommended.Results Among the 5898 cases,32 have failed for the initial NIPT,including 17 cases with substandard cffDNA%,10 cases with data fluctuation after twice library constructing and sequencing,and 5 cases with unidentifiable sex chromosome abnormalities.For these 32 cases,2 directly underwent amniocentesis,and karyotyping analysis showed both were normal.Six of the 30 redrawn cases finally turned out to be nonreportable.The final nonreportable rate was therefore 0.1%(8/5898).Of the redrawn cases,1 trisomy 21,1 trisomy 18 and 1 trisomy 13 high risk-cases were identified,which were all confirmed to be false positive.Among the 6 nonreportable cases,2 women underwent invasive prenatal testing,and 1 was found to have a normal fetal karyotype,while another was found to have an abnormal karyotype of mos45,X[32]/46,XY[18].The other 4 nonreportable cases who did not accept invasive prenatal testing have all reported normal child development at follow-up.Conclusion The main reason for nonreportable NIPT results was low cffDNA%.The high success rate of the redrawn cases has effectively increased the overall NIPT success rate and reduced the number of the cases necessitating invasive prenatal diagnosis.The initially nonreportable women may consider retesting after careful counseling with informed consent.