Brady Jeff, Wilson Lesley, McGregor Lynda, Valente Edward, Orning Lars
Axis-Shield Diagnostics, Ltd., Dundee, Scotland, UK.
Clin Chem. 2008 Mar;54(3):567-73. doi: 10.1373/clinchem.2007.096784. Epub 2008 Jan 4.
Conventional tests for vitamin B(12) deficiency measure total serum vitamin B12, whereas only that portion of vitamin B12 carried by transcobalamin (holotranscobalamin) is metabolically active. Measurement of holotranscobalamin (holoTC) may be more diagnostically accurate for detecting B(12) deficiency that requires therapy. We developed an automated assay for holoTC that can be used on the Abbott AxSYM immunoassay analyzer.
AxSYM Active B12 is a 2-step sandwich microparticle enzyme immunoassay. In step 1, a holoTC-specific antibody immobilized onto latex microparticles captures holoTC in samples of serum or plasma. In step 2, the captured holoTC is detected with a conjugate of alkaline phosphatase and antiTC antibody.
Neither apoTC nor haptocorrin exhibited detectable cross-reactivity. The detection limit was < or = 0.1 pmol/L. Within-run and total imprecision (CV ranges) were 3.4%-5.1% and 6.3%-8.5%, respectively. Assay CVs were < 20% from at least 3 pmol/L to 107 pmol/L. With diluted serum samples, measured concentrations were 104%-114% of the expected values in the working range of the assay. No interference from bilirubin, hemoglobin, triglycerides, erythrocytes, rheumatoid factor, or total protein was detected at expected (abnormal) concentrations. A comparison of the AxSYM Active B12 assay with a commercial RIA for holoTC yielded the regression equation: AxSYM = 0.98RIA + 4.7 pmol/L (S(y x), 11.4 pmol/L; n = 204). Assay throughput was 45 tests/h. A 95% reference interval of 19-134 pmol/L holoTC was established with samples from 292 healthy individuals.
The AxSYM Active B12 assay allows rapid, precise, sensitive, specific, and automated measurement of human holoTC in serum and plasma.
维生素B12缺乏的传统检测方法测量的是血清总维生素B12，而只有转钴胺素携带的那部分维生素B12（全转钴胺素）具有代谢活性。测量全转钴胺素（holoTC）对于检测需要治疗的维生素B12缺乏可能在诊断上更准确。我们开发了一种可用于雅培AxSYM免疫分析仪的全转钴胺素自动化检测方法。
AxSYM活性B12检测是一种两步夹心微粒酶免疫测定法。第一步，固定在乳胶微粒上的全转钴胺素特异性抗体捕获血清或血浆样本中的全转钴胺素。第二步，用碱性磷酸酶与抗转钴胺素抗体的结合物检测捕获的全转钴胺素。
脱辅基转钴胺素和钴胺素结合蛋白均未表现出可检测到的交叉反应性。检测限≤0.1 pmol/L。批内和总不精密度（CV范围）分别为3.4% - 5.1%和6.3% - 8.5%。在至少3 pmol/L至107 pmol/L的范围内，检测CV＜20%。对于稀释的血清样本，在检测的工作范围内，测量浓度为预期值的104% - 114%。在预期（异常）浓度下，未检测到胆红素、血红蛋白、甘油三酯、红细胞、类风湿因子或总蛋白的干扰。将AxSYM活性B12检测与一种用于全转钴胺素的商业放射免疫分析（RIA）进行比较，得到回归方程：AxSYM = 0.98RIA + 4.7 pmol/L（S(y x)，11.4 pmol/L；n = 204）。检测通量为45次检测/小时。用来自292名健康个体的样本建立了全转钴胺素的95%参考区间为19 - 134 pmol/L。
AxSYM活性B12检测可对血清和血浆中的人全转钴胺素进行快速、精确、灵敏、特异且自动化的测量。
