Screening-Labor Hannover, Hannover, Germany.
Clin Chim Acta. 2013 Jun 5;421:41-5. doi: 10.1016/j.cca.2013.03.001. Epub 2013 Mar 13.
Metabolic screening including newborn screening requires further differentiation of C5-acylcarnitines in order to separate different metabolic disorders and to detect interferents like pivalic acid originating from antibiotics.
For individual quantification of C5-acylcarnitine isoforms in dried blood spots we combined UPLC using a C18 column and gradient elution with tandem mass spectrometry in ESI+mode.
Results were linear, coefficients of determination (R(2))>0.9977, intra- and inter-assay coefficients of variations <5.2%, recovery 96.8-105.2%, limits of detection and quantitation <0.2 μmol/L. Out of 29.309 blood samples of the isolated population of the Faroe Islands 56 exceeded the cut-off of 0.5 μmol/L for C5-acylcarnitine; 45 of which could be retested using the method described. Pivaloylcarnitine was identified in 43 samples, isovalerylcarnitine was found in two samples.
The method was developed to allow direct re-analysis of samples showing elevated concentrations of C5-acylcarnitines in a metabolic screening program based on quantification of acylcarnitines after butylation. The technique should be especially useful in newborn screening for exclusion of false positives and for differentiation between isovaleric acidemia and 2-methylbutyryl-CoA dehydrogenase deficiency.
代谢筛查，包括新生儿筛查，需要进一步区分 C5-酰基肉碱，以便区分不同的代谢紊乱，并检测来自抗生素的干扰物，如异戊酸。
为了在干血斑中对 C5-酰基肉碱异构体进行个体定量，我们结合了使用 C18 柱的 UPLC 和 ESI+模式下的串联质谱进行梯度洗脱。
结果呈线性，决定系数（R(2)）>0.9977，日内和日间变异系数<5.2%，回收率为 96.8-105.2%，检测限和定量限<0.2 μmol/L。在法罗群岛隔离人群的 29,309 份血样中，有 56 份超过了 0.5 μmol/L 的 C5-酰基肉碱 cutoff 值；其中 45 份可以使用所描述的方法进行重新测试。在 43 个样本中鉴定出了异戊酰肉碱，在 2 个样本中发现了异丁酰肉碱。
该方法旨在允许在基于丁酰化后酰基肉碱定量的代谢筛查方案中，对显示 C5-酰基肉碱浓度升高的样品进行直接重新分析。该技术在新生儿筛查中特别有用，可以排除假阳性，并区分异戊酸血症和 2-甲基丁酰辅酶 A 脱氢酶缺乏症。
