Metabolic Biochemistry Department, Pitié Salpêtrière University Hospital, AP-HP, Paris, France.
Clinical Chemistry Department, Inherited Metabolic Diseases, CHU Bordeaux, 33076 Bordeaux, France.
Clin Chim Acta. 2019 Jun;493:148-155. doi: 10.1016/j.cca.2019.03.007. Epub 2019 Mar 9.
Cerebral Creatine deficiency syndromes (CCDS) include three hereditary diseases affecting the metabolism of creatine (Cr): arginine glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency and disorders of creatine transporter. These pathologies cause a brain creatine deficiency responsible of non-specific neurological impairments with mental retardation. LC-MS/MS measurements of guanidinoacetic acid (GAA) and creatine in urine and plasma are an important screening test to identify the deficit. Analysis of this polar and basic molecules not hold on standard column requires a derivatization step to butyl-esters. To overcome this long and fastidious derivatization, an ion pairing (IP) method was chosen in this study.
IP method was validated using Comité francais d'accréditation (COFRAC) recommendations. Then, urine GAA and creatine of 15 patients with a CDS deficiency suspected were tested y LC-MS/MS using IP technique, and performances were assessed with reference laboratory method (butylation method). Moreover, references values were suggested y the study of 100 urines samples of healthy patients.
The method developed provided a good accuracy and precision with intra and inter-day coefficients of variation (CVs) <15%. The curve was linear for the biological and pathological concentrations. The comparison with the reference method did not reveal any significant difference for analytical performances but showed a simplification of the preparation of samples.
The use of IP technique that we have developed demonstrated a good correlation with the butylation method. Moreover, this new method not only allows a simplification of the technique, but also decreases in run time.
脑肌酸缺乏综合征（CCDS）包括三种影响肌酸（Cr）代谢的遗传性疾病：精氨酸甘氨酸酰胺转移酶缺乏症、鸟氨酸氨甲酰转移酶缺乏症和肌酸转运蛋白紊乱。这些病理导致脑肌酸缺乏，引起非特异性神经损伤和智力迟钝。尿液和血浆中胍基乙酸（GAA）和肌酸的 LC-MS/MS 测量是识别缺陷的重要筛选试验。对这种极性和碱性分子的分析不能在标准柱上进行，需要进行丁酯衍生化步骤。为了克服这种冗长而繁琐的衍生化，本研究选择了离子对（IP）方法。
根据法国认可委员会（COFRAC）的建议验证了 IP 方法。然后，使用 IP 技术对 15 例疑似 CDS 缺乏症患者的尿液 GAA 和肌酸进行 LC-MS/MS 检测，并与参考实验室方法（丁酯化法）评估性能。此外，通过对 100 例健康患者尿液样本的研究，提出了参考值。
所开发的方法提供了良好的准确度和精密度，日内和日间变异系数（CVs）<15%。该曲线在生物和病理浓度范围内呈线性。与参考方法的比较并未显示分析性能有任何显著差异，但显示出样品制备的简化。
我们开发的 IP 技术与丁酯化法具有良好的相关性。此外，这种新方法不仅简化了技术，而且缩短了运行时间。
