Biochemical Sciences, Viapath, St Thomas' Hospital, London, UK.
GKT School Medical Education, Kings College London, London, UK.
Ann Clin Biochem. 2020 Jul;57(4):277-290. doi: 10.1177/0004563220933303.
Plasma amino acid analysis is key to the diagnosis and monitoring of inherited disorders of amino acid synthesis, catabolism and transport. Ion exchange chromatography (IEC) is widely accepted as the gold standard method of analysis, but with the introduction of liquid chromatography tandem mass spectrometry (LC-MS/MS) and liquid chromatography mass spectrometry (LC-MS) methods, this should now be questioned.
The analytical performance of three commercially available reagent kits, Waters AccQ Tag™ ULTRA LC-MS, SpOtOn Amino Acids LC-MS/MS and Chromsystems MassChrom® Amino Acid Analysis LC-MS/MS, were evaluated and compared with Biochrom Physiological Amino Acids ion exchange chromatography. Correlation with IEC was assessed by Passing-Bablok regression, concordance correlation coefficients (CCC) and Bland-Altman analysis for 21 common amino acids. Calculation of the total error from imprecision and bias was also used to benchmark performance.
The MassChrom® and SpOtOn kits demonstrated acceptable inter-batch imprecision (CV < 10%) and accuracy (mean bias < 10%), whereas the AccQ Tag™ ULTRA kit did not. Good correlation (CCC > 0.95) with Biochrom IEC was demonstrated for 10/21 analytes in both the MassChrom® and SpOtOn kits and 6/21 in the AccQ Tag™ ULTRA kit.
The LC-MS assay demonstrated variable analytical performance and correlated poorly with ion exchange chromatography. Both LC-MS/MS assays demonstrated comparable analytical performance and reasonable correlation with ion exchange chromatography. They also confer practical advantages which cannot be realized by ion exchange chromatography, superior specificity and significantly faster analysis time, suggesting that ion exchange chromatography should no longer be described as the gold standard method for plasma amino acid analysis.
血浆氨基酸分析是诊断和监测氨基酸合成、分解和转运遗传障碍的关键。离子交换色谱（IEC）被广泛认为是分析的金标准方法，但随着液相色谱串联质谱（LC-MS/MS）和液相色谱-质谱（LC-MS）方法的引入，这一观点现在应该受到质疑。
评估并比较了三种市售试剂试剂盒，Waters AccQ Tag ULTRA LC-MS、SpOtOn 氨基酸 LC-MS/MS 和 Chromsystems MassChrom 氨基酸分析 LC-MS/MS 的分析性能，并与 Biochrom 生理氨基酸离子交换色谱进行比较。通过 Passing-Bablok 回归、一致性相关系数（CCC）和 Bland-Altman 分析评估与 IEC 的相关性，用于 21 种常见氨基酸。还使用来自不精密度和偏差的总误差计算来基准性能。
MassChrom 和 SpOtOn 试剂盒表现出可接受的批间不精密度（CV<10%）和准确度（平均偏差<10%），而 AccQ Tag ULTRA 试剂盒则不然。MassChrom 和 SpOtOn 试剂盒中的 10/21 种分析物以及 AccQ Tag ULTRA 试剂盒中的 6/21 种分析物与 Biochrom IEC 具有良好的相关性（CCC>0.95）。
LC-MS 测定法表现出可变的分析性能，与离子交换色谱相关性差。两种 LC-MS/MS 测定法均表现出可比的分析性能和与离子交换色谱的合理相关性。它们还具有离子交换色谱无法实现的实际优势，即更高的特异性和显著更快的分析时间，这表明离子交换色谱不应再被描述为血浆氨基酸分析的金标准方法。
