质谱技术检测羊水中代谢物产前诊断甲基丙二酸血症

Prenatal diagnosis of methylmaionic acidemia by amniotic fluid metabolites analysis using mass spectrometry

目的探讨串联质谱及气相色谱质谱技术检测羊水中的酰基肉碱及有机酸用于甲基丙二酸血症（methylmalonic acidemia，MMA）产前诊断的效果。方法2007年10月11日至2014年12月20日，131例孕妇因为生育过MMA患儿就诊于上海交通大学医学院附属新华医院，要求行MMA产前诊断（病例组）。从同期进行常规产前诊断孕妇中随机选取120例作为对照组。2组孕妇均于妊娠16—20周行羊膜腔穿刺术抽取羊水，并采用串联质谱技术检测羊水丙酰肉碱和乙酰肉碱水平，采用气相色谱质谱技术检测羊水甲基丙二酸和甲基枸橼酸水平。病例组中80例先证者基因诊断明确的病例同时行羊水细胞基因检测。采用Wilcoxon秩和检验进行统计学分析。结果病例组中29例孕妇羊水丙酰肉碱、丙酰肉碱／乙酰肉碱、甲基丙二酸及甲基枸橼酸水平高于正常参考值，胎儿MMA阳性，检出率为22．1％。29例MMA阳性胎儿孕妇的羊水丙酰肉碱水平、丙酰肉碱／乙酰肉碱明显高于对照组[8．13（2．42～16．70）与1．04（0．52～3．40）μmol／L，0．77（0．30～1．79）与0．10（0．05～0．22），Z值分别为-8．313和-8．374，P值均〈0．05]；甲基丙二酸、甲基枸-酸水平也高于对照组[9．13（1．68～61．78）与0．00（0．00～1．31）mmol／mol肌酐，0．58（0．00-1．90）与0．05（0．00～0．52）mmol／mol肌酐，Z值分别为-11．348及-6．632，P值均〈0．051。其余102例孕妇丙酰肉碱、丙酰肉碱／乙酰肉碱、甲基丙二酸及甲基枸橼酸水平不高于正常参考值（胎儿MMA阴性），且与对照组比较差异无统计学意义（P值均〉0．05），但低于MMA阳性胎儿（P值均〈0．05）。病例组29例MMA阳性胎儿中16例进行了基因检测，诊断MUT型MMA5例，MMACHC型MMA11例。其余102例MMA阴性胎儿中64例行基因检测，其中44例检测到1个突变位点，提示胎儿为MMA杂合子；另20例未检测到突变位点。质谱检测结果与基因检测结果符合率为100％（80／80）。结论串联质谱及气相色谱质谱技术检测羊水中的丙酰肉碱、甲基丙二酸及甲基枸橼酸水平，可对先证者为MMA的孕妇进行产前诊断。

Objective To investigate the effect of tandem mass spectrometry and gas chromatography-mass spectrometry to make prenatal diagnosis of methylmalonic acidemia （MMA） by detecting organic acid and acylcarnitine in amniotic fluid. Methods From October 11, 2007 to December 20, 2014, 131 pregnant women with MMA proband received prenatal diagnosis of MMA in Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine （case group）. Another 120 cases of pregnant women for conventional prenatal diagnosis at the same period were as control group. The pregnant women of two groups had the amniocentesis at 16 to 20 weeks of gestation. The levels of propionylcarnitine（C3） and acetylcarnitine（C2） in amniotic fluid were detected by tandem mass spectrometry. The methylmalonic acid and methylcitrate acid were detected by gas chromatography-mass spectrometry. MMA gene of cells in amniotic fluid of eighty fetuses with proband clearly diagnosed were detected by gene testing. Data were analyzed by Wilcoxon test. Results In case group, 29 fetuses were found positive for higher level of C3, C3/C2, methylmalonic acid and methylcitrate acid compared with normal reference value, and the detected rate of fetal MMA was 22.1%（29/131）. The levels of C3 and C3 / C2 in amniotic fluid of these 29 cases were higher than those in control group[8.13（2.42-16.70） vs 1.04（0.52-3.40） μmol/L, Z = -8.313; 0.77（0.30-1.79） vs 0.10（0.05- 0.22）, Z= - 8.374; P 〈 0.05 respectively]. The levels of methylmalonic acid and methylcitrate acid were also higher[9.13（1.68-61.78） vs 0.00（0.00-1.31） mmol/mol Crea, Z= - 11.348; 0.58（0.00-1.90） vs 0.05（0.00-0.52） mmol/mol Crea, Z= - 6.632, P 〈 0.05 respectively].For the other 102 cases in case group, the levels of C3, C3/C2, methylmalonic acid and methylcitrate acid were not higher than normal reference value, and were similar to those in control group （P 〉 0.05）; while they were lower than those of positive MMA fetuses （all P 〈 0.05）. Among 29 positive fetuses, 16 fetuses were detected MMA gene, five were diagnosed as MUT forms of MMA and 11 were MMACHC forms of MMA. In 102 MMA negative fetuses, 64 fetuses were detected MMA gene, 44 were found one mutant site and 20 were found no gene mutation. The coincidence rate between gene detecting and mass spectrometry was 100%（80/80）. Conclusions Mass spectrometry could be used to measure the C3, methylmalonic acid and methylcitrate acid levels in amniotic fluid of pregnant women with MMA proband to make prenatal diagnosis.