Freeto Scott, Mason Donald, Chen Jie, Scott Robert H, Narayan Srinivas B, Bennett Michael J
Waters Corporation, Milford, MA, USA.
Ann Clin Biochem. 2007 Sep;44(Pt 5):474-81. doi: 10.1258/000456307781646012.
Patients with inherited disorders of amino acid metabolism including maple syrup urine disease, tyrosinaemia and phenylketonuria on dietary management require frequent monitoring of disease-relevant plasma amino acids in order to optimize therapeutic benefit. Poorly controlled maple syrup urine disease in particular may result in catastrophic metabolic decompensation. Most methods for monitoring amino acid concentrations are time-consuming and have clinically impractical turnaround times, particularly when the required time to run standards and control samples is taken into account.
We have analysed plasma amino acids using standard ion-exchange chromatography with ninhydrin detection in an amino acid analyser and compared the data with that obtained for the same samples using ultra-performance liquid chromatography (UPLC) separation with detection by tandem mass spectrometry.
The two methodologies compared very well for the measurement of six important amino acids with correlation coefficients greater than 0.96 for all. The time for sample preparation was longer for the UPLC methodology as batched derivatization and evaporation is required but UPLC-tandem mass spectrometry generated sample results every 8 min while conventional ion-exchange chromatography took almost 1 h per sample.
UPLC-tandem mass spectrometry generates data that compares well with existing 'gold standard' methodologies but significantly reduces sample turnaround time. Decreasing the turnaround time for amino acid analyses is very likely to improve clinical care for patients with amino acid disorders as dietary adjustments can be made sooner.
患有遗传性氨基酸代谢紊乱疾病（包括枫糖尿症、酪氨酸血症和苯丙酮尿症）的患者在进行饮食管理时，需要频繁监测与疾病相关的血浆氨基酸水平，以优化治疗效果。特别是枫糖尿症控制不佳可能导致灾难性的代谢失代偿。大多数监测氨基酸浓度的方法耗时较长，临床周转时间不切实际，尤其是考虑到运行标准品和对照样品所需的时间时。
我们使用氨基酸分析仪中的茚三酮检测标准离子交换色谱法分析血浆氨基酸，并将数据与使用超高效液相色谱（UPLC）分离并通过串联质谱检测的相同样品的数据进行比较。
两种方法在测量六种重要氨基酸方面表现非常相似，所有氨基酸的相关系数均大于0.96。UPLC方法的样品制备时间较长，因为需要批量衍生化和蒸发，但UPLC串联质谱每8分钟生成一次样品结果，而传统离子交换色谱法每个样品需要近1小时。
UPLC串联质谱法生成的数据与现有的“金标准”方法相当，但显著缩短了样品周转时间。缩短氨基酸分析的周转时间很可能改善氨基酸紊乱患者的临床护理，因为可以更快地进行饮食调整。
