血清游离轻链检测：κ/λ 比值升高。

Serum Free Light Chain Assay: Shift Toward a Higher κ/λ Ratio.

机构信息

University Institute of Clinical Chemistry, Bern University Hospital, and University of Bern, Bern, Switzerland.

Center of Laboratory Medicine, Switzerland.

出版信息

J Appl Lab Med. 2020 Jan 1;5(1):114-125. doi: 10.1093/jalm.2019.029330.

DOI:10.1093/jalm.2019.029330

PMID:32445339

Abstract

BACKGROUND

The analysis of serum free light chains (FLCs) is clinically relevant for the diagnosis and therapeutic management of clonal plasma cell disorders. This study compares the performance of monoclonal and polyclonal FLC κ and λ assays in clinical samples determined in a single academic center.

METHODS

Serum FLCs were analyzed from 102 patients using the Freelite (Binding Site) and N Latex (Siemens) assays on the BN ProSpec System (Siemens). When available, data for protein electrophoresis, immunofixation, C-reactive protein, and estimated glomerular filtration rate (eGFR) were combined with FLC results to evaluate performance.

RESULTS

Method evaluation showed acceptable imprecision and inaccuracy measures of <4.4% and 12.9%, respectively. Poor agreement between the methods was observed, including constant and proportional bias and poor correlation (Kendall τ, 0.671-0.901). The N Latex assay was not affected by the renal impairment estimated by eGFR, unlike the FLC κ/λ ratio results by the Freelite assay. With the Freelite assay, 98% of putative controls without monoclonal gammopathy (n = 42) showed a κ/λ ratio that was above the median of the standard diagnostic range or renal diagnostic range. A shift toward higher κ/λ ratios was also observed when retrospective data between 2011 and 2017 were compared.

CONCLUSIONS

Unlike the Freelite assay, κ/λ ratios analyzed with the N Latex assay were not affected by renal failure. Both methods showed acceptable performances using nephelometry, but they were poorly correlated. A shift toward κ/λ ratios might impair the specificity of borderline increased κ/λ results. This should be considered when interpreting FLC κ and λ results.

摘要

背景

血清游离轻链（FLC）分析对于克隆性浆细胞疾病的诊断和治疗管理具有重要的临床意义。本研究比较了单克隆和多克隆 FLC κ 和 λ 检测在单一学术中心临床样本中的性能。

方法

使用 BN ProSpec 系统（西门子）上的 Freelite（Binding Site）和 N Latex（西门子）检测试剂盒，对 102 例患者的血清 FLC 进行分析。当有条件时，将蛋白电泳、免疫固定、C 反应蛋白和估计肾小球滤过率（eGFR）的数据与 FLC 结果相结合，以评估性能。

结果

方法评估显示，<4.4%和 12.9%的不精密度和不准确度测量值均在可接受范围内。两种方法之间观察到一致性较差，包括恒定和比例偏差以及相关性差（Kendall τ，0.671-0.901）。与 Freelite 检测试剂盒的 FLC κ/λ 比值结果不同，N Latex 检测试剂盒不受 eGFR 估计的肾功能损害影响。使用 Freelite 检测试剂盒，98%的无单克隆丙种球蛋白病的假定对照（n=42）显示 κ/λ 比值高于标准诊断范围或肾脏诊断范围的中位数。当比较 2011 年至 2017 年的回顾性数据时，还观察到 κ/λ 比值向更高比值的偏移。