甲基丙二酸血症患者血串联质谱及尿气相色谱质谱检测分析

Analysis of propinoylcarnitine in blood and methylmalonic acid in urine of 162 patients withmethylmalonic acidemia

目的探讨甲基丙二酸血症（MMA）患者尿甲基丙二酸、甲基枸橼酸水平及血丙酰肉碱（C3）水平、丙酰肉碱与乙酰肉碱的比值（C3／C2）的变化及其在MMA诊断中的应用价值。方法分析2003年12月至2012年3月上海交通大学附属新华医院确诊的162例MMA患者及200名健康儿童（对照组）尿甲基丙二酸、甲基枸橼酸及血C3水平、C3／C2变化，已明确分型的患者分为单纯型MMA组（n=51）和MMA合并同型半胱氨酸血症组（合并型MMA组）（n=65）；尿甲基丙二酸及甲基枸橼酸水平采用气相色谱质谱检测，血C2、C3及蛋氨酸（Met）水平采用串联质谱技术检测。结果MMA患者尿甲基丙二酸和甲基枸橼酸水平分别为259．10（6．73～6429．28）和4．39（0～248．96），血C3和C3／C2中位数（范围）分别为8．52（1．50～52．11）μmol／L和0．73（0．28～2．89），均高于参考值（分别为0．2～3．6、0～1．1、0．50～4．00μmol／L、0．04～0．25），且显著高于对照组[分别为0（0～1．87）、0．10（0～1．84），1．40（0．53～3．90）p．mol／L、0．10（0．04～0．23），均P〈0．01]。其中15例患者血c3水平正常，而C3／C2及尿甲基丙二酸水平均增高。合并型MMA组血蛋氨酸水平低于参考值和单纯型MMA患者组及对照组[8．71（0．68～31．95）μmol／L比10．00～35．00μmol／L、15．35（4．18～59．50）μmol／L、15．59（10．20～34．68）μmol／L，均P〈0．05]。结论尿甲基丙二酸及血C3／C2显著增高对诊断MMA具有特异性，诊断MMA需将两种检测方法结合以减少漏诊及误诊。尿甲基丙二酸及血C3／C2轻度增高者需反复送检或基因检测确诊。

Objective To analyze the levels of methylmalonic acid and methylcitric acid in urine, propinoylcarnitine （C3） in plasma and C3/acetylcarnitine （C2） of patients with methylmalonie acidemia （MMA） and explore their applications in the diagnosis of MMA. Methods From December 2003 to March 2012, a total of 162 patients with MMA （MMA group） and 200 healthy children （control group） of Xinhua Hospital, Shanghai Jiaotong University School of Medicine were recruited. MMA patients with a definite classification were divided into 2 groups： isolate MMA group （ n = 51 ） and MMA complicated with homocysteinemia group （ n = 65 ）. Gas chromatography-mass spectrometry was used to measure the urine levels of methylmalonic acid and methylcitric acid and tandem mass spectrometry to measure the blood levels of free carnitine （C0） , acylcamitines and methionine （Met）. Results In the MMA group, the median levels of methylmalonic acid （ 259. 10 （ 6. 73 - 6429. 28 ） ）, methylcitric acid （ 4. 39 （ 0 - 248.96 ） ）, C3 （ 8. 52 （ 1.50 - 52. 11 ） μmol/L） and C3/C2 （ 0. 73 （ 0. 28 - 2. 89 ） ） were all higher than the upper limit values（0. 2 -3.6, 0 - 1.1,0. 50 -4. 00 μmo]/L and 0. 04 -0. 25 respectively）. And they were all higher than those in the control group （0 （0 - 1.87）, 0. 10 （0 - 1.84）, 1.40 （0. 53 - 3.90）μmo]/L, 0. 10 （0. 04-0. 23）, all P 〈0. 01）. C3/C2 increased significantly in 15 patients while the C3 level remainednormal. The median level of Met was normal in the isolate MMA group. But in patients with homocysteinemia, the level of 8.71 （0. 68 -31.95 ）μmol/L was below the reference value （10. 00 - 35.00 μmol/L） and lower than that in the isolate MMA group（ 15.35 （4. 18 -59.50）μmol/L）and the control group（15.59（10.20-34.68） μmol/L, all P〈0.05）. Conclusions Significant increases in the urine level of methylmalonic acid and C3/C2 may be specific to MMA. Organic acid analyses of gas chromatography-mass spectrometry and acylcarnitines with tandem mass spectrometry are required for a definite diagnosis of this disorder. And repeated tests and genomic mutation analysis are necessary for patients with mildly abnormal biochemical indices.