Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, TheNetherlands.
Deparment of Clinical Chemistry, OLVG, Amsterdam, TheNetherlands.
Clin Chem Lab Med. 2018 Jun 27;56(7):1169-1175. doi: 10.1515/cclm-2017-0817.
The heavy/light chain (HLC) immunoassay quantifies the different heavy chain/light chain combinations of each immunoglobulin (Ig) class. This makes the HLC assay suited to quantify monoclonal immunoglobulins (M-protein) and for monitoring of patients with monoclonal gammopathies. This method is particularly advantageous for those samples in which electrophoretic quantification of the M-protein is not possible.
In this study we tested the analytical performance of the HLC assay in 166 routine clinical samples and in 27 samples derived from the Dutch external quality assessment (EQA) for M-protein diagnostics (74 participating laboratories). Analytical accuracy was assessed by verification that the sum of the HLC-pairs equaled total Ig concentration. Sensitivity of the HLC assay was determined in a direct method comparison with immunofixation electrophoresis (IFE).
Comparison of HLC data with routine Ig diagnostics in 27 EQA samples showed very good correlation for both the quantification of polyclonal and monoclonal IgG, IgA and IgM (Pearson correlations [r] were 0.94, 0.99 and 0.99, respectively; slopes were 0.94, 1.07 and 0.98, respectively). The overall concordance between IFE and the HLC ratio was high (93%) with a Cohen κ coefficient of 0.84. Discrepancies between both assays were mainly caused by the higher sensitivity of IFE to detect monoclonality.
We conclude that the HLC assay is an accurate method to quantify M-proteins that can improve monitoring of M-proteins in the beta fraction that cannot be quantified using electrophoretic techniques.
重链/轻链（HLC）免疫分析定量测定每个免疫球蛋白（Ig）类别的不同重链/轻链组合。这使得 HLC 分析适合定量单克隆免疫球蛋白（M 蛋白）并监测单克隆丙种球蛋白病患者。该方法特别适用于那些不能通过电泳定量 M 蛋白的样本。
在这项研究中，我们在 166 例常规临床样本和 27 例来自荷兰 M 蛋白诊断外部质量评估（EQA）的样本中测试了 HLC 分析的分析性能（74 个参与实验室）。通过验证 HLC 对的总和等于总 Ig 浓度，评估分析准确性。通过与免疫固定电泳（IFE）的直接方法比较，确定 HLC 分析的灵敏度。
在 27 份 EQA 样本中，将 HLC 数据与常规 Ig 诊断进行比较，均显示出很好的相关性，无论是对多克隆和单克隆 IgG、IgA 和 IgM 的定量（Pearson 相关系数[r]分别为 0.94、0.99 和 0.99；斜率分别为 0.94、1.07 和 0.98）。IFE 和 HLC 比值之间的总体一致性很高（93%），Cohen κ 系数为 0.84。两种检测方法之间的差异主要是由于 IFE 检测单克隆性的灵敏度更高。
我们得出结论，HLC 分析是一种定量 M 蛋白的准确方法，可以改善对无法通过电泳技术定量的β馏分中的 M 蛋白的监测。
