Department of Medical Genetics, Wilhelmina Children's Hospital, University Medical Centre (UMC) Utrecht, Utrecht, The Netherlands.
Department of Paediatric Gastroenterology and Metabolic Diseases, Wilhelmina Children's Hospital, UMC Utrecht, The Netherlands.
Anal Chim Acta. 2015 Jan 1;853:435-441. doi: 10.1016/j.aca.2014.10.043. Epub 2014 Oct 31.
Methylmalonic acid (MMA) and total homocysteine (tHCYS) concentrations are used to detect acquired and inborn errors of cobalamin (vitamin B12, Cbl) metabolism and to evaluate the effect of therapeutic interventions. Dried blood spot sampling offers a patient-friendly and easy alternative to plasma sampling. However, dried blood spot concentrations are not necessarily equal to plasma concentrations. Therefore, the objective of this work was to establish the relationship between MMA and tHYS dried blood spot and plasma concentrations to facilitate clinical implementation of dried blood spot sampling. MMA and tHCYS in both plasma and DBS were validated on ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). While position of the punch (in DBS) did affect tHCYS concentration, no influence of hematocrit (Ht) and blood volume on both MMA and tHCYS concentrations was observed. The plasma assay performed better than the DBS assay by most criteria. However, the DBS matrix was superior for tHCYS stability. Paired plasma and DBS samples were obtained from patients suspected for Cbl deficiency and from patients with a known inborn error of metabolism affecting MMA or tHCYS concentration. Based on the strong correlation of tHCYS in both matrices (y=0.46±1.12 (r(2)=0.91)), determination of tHCYS in plasma can be replaced by tHCYS in DBS. However, for MMA, a correlation in the higher (pathological) range of MMA exist, but no correlation was observed in the lower ranges. Therefore the added value of MMA concentrations in DBS is currently unknown and should be further investigated.
甲基丙二酸（MMA）和总同型半胱氨酸（tHCYS）浓度用于检测后天和先天钴胺素（维生素 B12，Cbl）代谢错误，并评估治疗干预的效果。干血斑采样为患者提供了一种方便且易于接受的血浆采样替代方法。然而，干血斑浓度不一定与血浆浓度相等。因此，这项工作的目的是建立 MMA 和 tHYS 干血斑和血浆浓度之间的关系，以促进干血斑采样的临床应用。MMA 和 tHCYS 在血浆和 DBS 中均通过超高效液相色谱-串联质谱（UPLC-MS/MS）进行验证。虽然打孔位置（在 DBS 中）确实会影响 tHCYS 浓度，但未观察到血细胞比容（Ht）和血液量对 MMA 和 tHCYS 浓度的影响。血浆测定在大多数标准下优于 DBS 测定。然而，DBS 基质更适合 tHCYS 稳定性。从疑似 Cbl 缺乏的患者和已知影响 MMA 或 tHCYS 浓度的先天代谢错误的患者中获得了配对的血浆和 DBS 样本。基于两种基质中 tHCYS 的强相关性（y=0.46±1.12（r²=0.91）），可以用 DBS 中的 tHCYS 代替血浆中的 tHCYS 进行测定。然而，对于 MMA，在较高（病理）范围内存在相关性，但在较低范围内没有相关性。因此，目前尚不清楚 DBS 中 MMA 浓度的附加值，应进一步研究。
