系列遗传学检测法评估真性胎儿染色体嵌合体的价值

Clinical value of different genetic testing methods for detection of true fetal chromosome mosaicism

目的探讨染色体核型分析、染色体微阵列分析(chromosomal microarray analysis,CMA)及荧光原位杂交(fluorescence in situ hybridization,FISH)技术在真性胎儿染色体嵌合体产前诊断中的应用价值。方法2018年4月至2021年8月,有明确产前诊断指征并在中山大学附属第一医院行羊膜腔穿刺术或/和脐静脉穿刺术产前诊断的单胎妊娠孕妇共4071例,其中产前诊断为胎儿真性染色体嵌合体的40例孕妇纳入回顾性分析。分析其染色体核型分析、CMA及FISH结果及嵌合染色体分布、嵌合比例及妊娠结局。采用χ2检验进行统计学分析。结果(1)真性胎儿染色体嵌合体的检出率为0.98%(40/4071)。(2)性染色体嵌合体占42.5%(17/40),其他染色体嵌合体包括21、22、18、16、7、12、15、17和20号染色体及染色体平衡易位嵌合。(3)真性胎儿染色体嵌合体在羊水染色体核型分析中的检出率为77.4%(24/31);在羊水CMA中的检出率为76.7%(23/30);在脐血染色体核型分析中的检出率为10/19;在脐血CMA中的检出率为7/11。(4)40例孕妇中的20例行FISH验证(14例同时行羊水及脐血FISH验证,5例行羊水FISH验证,1例行脐血FISH验证),均证实嵌合体诊断。对于嵌合比例<30%的低比例嵌合体检出率,羊水FISH的检出率(14/19)高于羊水CMA的检出率[43.5%(10/23)],差异有统计学意义(χ2=3.88,P=0.049)。(5)40例孕妇中5例失访,18例选择终止妊娠,17例分娩。17例新生儿娩出后及生后6~24个月电话随访未见智力及生长发育异常。14例FISH验证嵌合比例<30%的孕妇,8例选择继续妊娠至分娩,生后随访未见智力及生长发育异常。结论对于产前诊断真性胎儿染色体嵌合体,性染色体嵌合体发生率最高。产前发现胎儿染色体嵌合体,FISH验证可提高诊断率,且可较精确确定嵌合比例。FISH、CMA与染色体核型分析的联合应用可显著提高染色体嵌合体的检出率,并较精确评估嵌合比例,对预后咨询有指导价值。

Objective To investigate the performance of chromosome karyotype,chromosomal microarray analysis(CMA)and fluorescence in situ hybridization(FISH)in prenatal diagnosis of true fetal chromosome mosaicism.Methods This retrospective study enrolled 40 women with true fetal chromosome mosaicism from 4071 singleton pregnant women who were indicated for and underwent amniocentesis or/and cordocentesis in the the First Affiliated Hospital of Sun Yat-sen University from April 2018 to August 2021.The results of chromosome karyotyping,CMA and FISH,the types of chromosomal mosaicism,mosaicism ratio and pregnancy outcomes were analyzed using Chi-square test.Results(1)The detection rate of true fetal mosaicism was 0.98%(40/4071).(2)Sex chromosome mosaicism accounted for 42.5%(17/40).Other chromosomal mosaicism involved chromosomes 21,22,18,16,7,12,15,17 and 20,as well as balanced chromosomal translocation.(3)The detection rate of true fetal mosaicism by chromosome karyotyping was 77.4%(24/31)from amniotic fluid samples and 10/19 from umbilical cord blood samples,while that data by CMA was 76.7%(23/30)and 7/11,respectively.(4)Of the 40 pregnant women with fetal chromosome mosaicism,FISH test was performed on 20 cases(14 cases were verified with both amniotic fluid and umbilical cord blood samples,five with amniotic fluid samples and one with umbilical cord blood sample),and all of the diagnosis of mosaicism were confirmed.For those with mosaicism ratio<30%,the detection rate by FISH was higher than that by CMA among amniotic fluid samples[14/19 vs 43.5%(10/23),χ2=3.88,P=0.049].(5)Among the 40 pregnant women,five were lost to follow-up;18 chose to terminate the pregnancy;and 17 continued the pregnancy to delivery.No abnormalities in mental or physical development were reported in the 17 neonates after birth or during on-line follow-up between 6 to 24 months old.Of the 14 pregnant women with mosaicism ratio<30%which confirmed by FISH,eight chose to continue the pregnancy,and no abnormalities in mental development or growth were found in the neonates.Conclusions In prenatal diagnosis of true fetal choromosome mosaicism,the incidence of sex chromosome mosaicism is the highest.FISH may improve the prenatal diagnosis rate of mosaicism and is more accurate in determining the mosaicism ratio.The combination of FISH,CMA and chromosome karyotyping would significantly improve the detection rate of chromosomal mosaicism and assess the mosaicism ratio more accurately,which is of great value in clinical consultation and evaluation of fetal prognosis.