Departments of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States.
Departments of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States.
Clin Chim Acta. 2015 Jan 15;439:68-70. doi: 10.1016/j.cca.2014.10.002. Epub 2014 Oct 13.
Different patterns between serum immunofixation electrophoresis (SIFE) and urine immunofixation electrophoresis (UIFE) happen occasionally and laboratorians should understand the mechanisms behind the differences and additional tests required for complicated cases.
We investigated a complicated multiple myeloma case that showed inconsistent patterns of SIFE and UIFE. To differentiate monoclonal proteins (M-proteins), the urine sample was treated with dithiothreitol to open up the IgA molecule and urine free light chain assay was used for free light chain analysis.
The patient's SIFE indicated 2 IgA λ and 1 IgM κ M-proteins, while UIFE revealed monoclonal free λ light chains and a suspicious monoclonal IgA κ protein. Subsequent treatment of the urine sample with dithiothreitol and urine free light chain assay demonstrated that the suspicious monoclonal IgA κ protein was actually a monoclonal IgA λ and a free κ light chain that had similar electrophoretic mobility.
The differences identified between SIFE and UIFE in this case are due to the limitation of immunofixation electrophoresis on different specimen types and intra-molecular disulfide bonds formation in IgA. The laboratorians must be cognizant of the strengths and limitations of the procedure being performed and the ancillary testing techniques available to solve the problem.
血清免疫固定电泳（SIFE）和尿液免疫固定电泳（UIFE）的结果偶尔会出现不一致的情况，检验人员应了解导致这种差异的机制以及复杂病例所需的额外检测。
我们研究了一例复杂的多发性骨髓瘤病例，其 SIFE 和 UIFE 的结果不一致。为了区分单克隆蛋白（M 蛋白），我们对尿液样本进行了二硫苏糖醇处理以打开 IgA 分子，并使用尿液游离轻链检测进行游离轻链分析。
患者的 SIFE 显示 2 种 IgA λ 和 1 种 IgM κ M 蛋白，而 UIFE 显示单克隆游离 λ 轻链和可疑的单克隆 IgA κ 蛋白。随后对尿液样本进行二硫苏糖醇处理和尿液游离轻链检测表明，可疑的单克隆 IgA κ 蛋白实际上是单克隆 IgA λ 和具有相似电泳迁移率的游离 κ 轻链。
本例中 SIFE 和 UIFE 之间的差异是由于免疫固定电泳在不同标本类型上的局限性以及 IgA 分子内二硫键的形成所致。检验人员必须了解所进行的检测程序的优势和局限性，以及可用的辅助检测技术来解决问题。
