Fulton Richard B, Fernando Suran L
PaLMS Immunorheumatology Laboratory, Royal North Shore Hospital, Reserve Road, St Leonards 2065, Sydney, Australia.
Ann Clin Biochem. 2009 Sep;46(Pt 5):407-12. doi: 10.1258/acb.2009.009038. Epub 2009 Jul 29.
The potential for serum free light chain (sFLC) assay measurements to replace urine electrophoresis (uEPG) and to also diminish the need for serum immunofixation (sIFE) in the screening for monoclonal gammopathy was assessed. A testing algorithm for monoclonal protein was developed based on our data and cost analysis.
Data from 890 consecutive sFLC requests were retrospectively analysed. These included 549 samples for serum electrophoresis (sEPG), 447 for sIFE, and 318 for uEPG and urine immunofixation (uIFE). A total of 219 samples had sFLC, sEPG, sIFE and uEPG + uIFE performed. The ability of different test combinations to detect the presence of monoclonal proteins was compared.
The sFLC kappa/lambda ratio (FLC ratio) indicated monoclonal light chains in 12% more samples than uEPG + uIFE. The combination of sEPG and FLC ratio detected monoclonal proteins in 49% more samples than the combination of sEPG and sIFE. Furthermore, the sEPG + FLC ratio combination detected monoclonal protein in 6% more samples than were detected by the combined performance of sEPG, sIFE, uEPG and uIFE. However, non-linearity of the assay, the expense of repeat determinations due to the narrow measuring ranges, and frequent antigen excess checks were found to be limitations of the sFLC assay in this study.
The FLC ratio is a more sensitive method than uIFE in the detection of monoclonal light chains and may substantially reduce the need for onerous 24 h urine collections. Our proposed algorithm for the evaluation of monoclonal gammopathy incorporates the sFLC assay, resulting in a reduction in the performance of labour intensive sIFE and uEPG + uIFE while still increasing the detection of monoclonal proteins.
评估了血清游离轻链（sFLC）检测在替代尿电泳（uEPG）以及减少单克隆丙种球蛋白病筛查中血清免疫固定电泳（sIFE）需求方面的潜力。基于我们的数据和成本分析，开发了一种单克隆蛋白检测算法。
回顾性分析了890例连续的sFLC检测申请数据。这些数据包括549例血清电泳（sEPG）样本、447例sIFE样本以及318例uEPG和尿免疫固定电泳（uIFE）样本。总共219例样本同时进行了sFLC、sEPG、sIFE以及uEPG + uIFE检测。比较了不同检测组合检测单克隆蛋白存在的能力。
sFLC κ/λ比值（FLC比值）显示单克隆轻链的样本比uEPG + uIFE多12%。sEPG与FLC比值的组合检测到单克隆蛋白的样本比sEPG与sIFE的组合多49%。此外，sEPG + FLC比值组合检测到单克隆蛋白的样本比sEPG、sIFE、uEPG和uIFE联合检测多出6%。然而，本研究发现该检测方法存在非线性、测量范围窄导致重复检测成本高以及频繁进行抗原过量检查等局限性。
FLC比值在检测单克隆轻链方面比uIFE更敏感，并且可能大幅减少繁琐的24小时尿液收集需求。我们提出的评估单克隆丙种球蛋白病的算法纳入了sFLC检测，在减少劳动强度大的sIFE和uEPG + uIFE检测的同时，仍增加了单克隆蛋白的检测率。
