Immunology Laboratory, CHU Timone AP-HM, Marseille, France.
Referral Centre for Neuromuscular Diseases and ALS, CHU Timone, Marseille, France.
Clin Chem Lab Med. 2023 Apr 6;61(9):1623-1629. doi: 10.1515/cclm-2022-0602. Print 2023 Aug 28.
Define the cutoff thresholds of the Kappa (K) and Lambda (L) free light chains (FLC) indices for the detection of intrathecal immunoglobulin synthesis (IIS) using the new K and L FLC ELISA from SEBIA. The reference technique, which is not readily standardized between laboratories, is based on the demonstration of oligoclonal banding (OCB) in cerebrospinal fluid (CSF) which is absent in serum. For the past 6 years, we have also routinely calculated the K FLC index using The Binding Site (TBS) reagents on an Optilite instrument, an approach increasingly used as an alternative and/or a complement to electrophoretic analysis.
We analyzed 391 serum/CSF pairs divided into three groups. The first group were cases without OCB and with normal albumin CSF/serum ratio (n=174). The second group were cases with specific OCB (n=73). The last group included patients with increased albumin CSF/sera ratio without OCB (n=142).
Analysis of the first group determined that the cutoffs for detection of IIS are respectively 2.55 and 1.02 for the K FLC and L FLC indices. Of the 73 cases with IIS, only 2 had a K FLC index below this threshold (sensitivity of 97.26%), while 16 out of 73 cases (78.08%) and 13 out of 72 cases (81.94%) had an IgG and L FLC index below the cutoffs, respectively. Additionally, we illustrate equivalent performances for prediction of the presence of OCB between SEBIA and TBS methods.
Sebia K FLC and L FLC assays are adequate alternative methods for the diagnosis of IIS.
使用 SEBIA 的新型 K 和 L 游离轻链（FLC）ELISA 定义 Kappa（K）和 Lambda（L）游离轻链指数（FLC）用于检测鞘内免疫球蛋白合成（IIS）的截断阈值。该参考技术在实验室之间不易标准化，其基础是脑脊液（CSF）中寡克隆带（OCB）的显示，而血清中不存在 OCB。在过去的 6 年中，我们还使用 Optilite 仪器上的 Binding Site（TBS）试剂常规计算 K FLC 指数，这种方法越来越多地被用作电泳分析的替代方法和/或补充方法。
我们分析了分为三组的 391 对血清/CSF 样本。第一组为无 OCB 且 CSF/血清白蛋白比值正常的病例（n=174）。第二组为有特异性 OCB 的病例（n=73）。最后一组包括无 OCB 但 CSF/血清白蛋白比值升高的患者（n=142）。
对第一组的分析确定，用于检测 IIS 的截断值分别为 2.55 和 1.02，用于 K FLC 和 L FLC 指数。在 73 例 IIS 患者中，只有 2 例 K FLC 指数低于该阈值（敏感性为 97.26%），而 73 例中有 16 例（78.08%）和 72 例中有 13 例（81.94%）的 IgG 和 L FLC 指数低于截断值。此外，我们还说明了 SEBIA 和 TBS 方法在预测 OCB 存在方面的等效性能。
SEBIA K 和 L FLC 测定法是 IIS 诊断的合适替代方法。
