Intrathecal production of kappa free light chains (KFLC) occurs in multiple sclerosis and can be measured using the KFLC index. KFLC index values can be determined more easily than oligoclonal bands (OB) detection and seem more sensitive than the immunoglobulin (Ig)G index to diagnose multiple sclerosis. We assessed the value of OB, KFLC index cut-offs 5.9, 6.6, and 10.61, and IgG index to diagnose multiple sclerosis with prospectively acquired data from a clinically isolated syndrome (CIS) inception cohort. We selected patients with sufficient data to determine OB positivity, MRI dissemination in space (DIS) and time (DIT), IgG index, and sufficient quantities of paired CSF and blood samples to determine KFLC indexes (n = 214). We used Kendall´s Tau coefficient to estimate concordance; calculated the number of additional diagnoses when adding each positive index to DIS and positive OB; performed survival analyses for OB and each index with the outcomes second attack and 2017 MRI DIS and DIT; and estimated the diagnostic properties of OB and the different indexes for the abovementioned outcomes at five years. OB were positive in 138 patients (64.5%), KFLC-5.9 in 136 (63.6%), KFLC-6.6 in 135 (63.1%), KFLC-10.61 in 126 (58.9%) and IgG index in 101 (47.2%). The highest concordance was between OB and KFLC-6.6 (τ=0.727) followed by OB and KFLC-5.9 (τ=0.716). Combining DIS plus OB or KFLC-5.9 increased the number of diagnosed patients by 11 (5.1%), with KFLC-6.6 by 10 (4.7%), with KFLC-10.61 by 9 (4.2%), and with IgG index by 3 (1.4%). Patients with positive OB or indexes reached second attack and MRI DIS and DIT faster than patients with negative results (P < 0.0001 except IgG index in second attack: P = 0.016). In multivariable Cox models [aHR (95% CI)], the risk for second attack was very similar between KFLC-5.9 [2.0 (0.9-4.3), P = 0.068] and KFLC-6.6 [2.1 (1.1-4.2), P = 0.035]. The highest risk for MRI DIS and DIT was demonstrated with KFLC-5.9 [4.9 (2.5-9.6), P < 0.0001], followed by KFLC-6.6 [3.4 (1.9-6.3), P < 0.0001]. KFLC-5.9 and KFLC-6.6 had a slightly higher diagnostic accuracy than OB for second attack (70.5, 71.1, and 67.8) and MRI DIS and DIT (85.7, 85.1, and 81.0). KFLC indexes 5.9 and 6.6 performed slightly better than OB to assess multiple sclerosis risk and in terms of diagnostic accuracy. Given the concordance between OB and these indexes, we suggest using DIS plus positive OB or positive KFLC index as a modified criterion to diagnose multiple sclerosis.

中文翻译：

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kappa 游离轻链指数和寡克隆带在 McDonald 标准中具有相似的作用

鞘内产生 kappa 游离轻链 (KFLC) 发生在多发性硬化症中，可以使用 KFLC 指数进行测量。KFLC 指数值比寡克隆带 (OB) 检测更容易确定，并且似乎比免疫球蛋白 (Ig)G 指数更灵敏地诊断多发性硬化症。我们评估了 OB、KFLC 指数截断值 5.9、6.6 和 10.61 以及 IgG 指数的价值，以使用从临床孤立综合征 (CIS) 初始队列中前瞻性获得的数据来诊断多发性硬化症。我们选择了具有足够数据的患者来确定 OB 阳性、MRI 空间传播 (DIS) 和时间 (DIT)、IgG 指数以及足够数量的配对 CSF 和血液样本以确定 KFLC 指数 (n = 214)。我们使用 Kendall 的 Tau 系数来估计一致性；计算将每个阳性指标添加到DIS和阳性OB时的附加诊断数；对 OB 和每个指标进行生存分析，结果为第二次发作和 2017 MRI DIS 和 DIT；并在五年内评估了 OB 的诊断特性和上述结果的不同指标。OB阳性138例（64.5%），KFLC-5.9阳性136例（63.6%），KFLC-6.6阳性135例（63.1%），KFLC-10.61阳性126例（58.9%），IgG指数阳性101例（47.2%）。最高的一致性在 OB 和 KFLC-6.6 (τ=0.727) 之间，其次是 OB 和 KFLC-5.9 (τ=0.716)。结合 DIS 加 OB 或 KFLC-5.9 诊断的患者人数增加了 11 人（5.1%），KFLC-6.6 增加了 10 人（4.7%），KFLC-10.61 增加了 9 人（4.2%），IgG 指数增加了 3（ 1.4%)。OB或指标阳性的患者比阴性结果的患者更快地达到第二次发作和MRI DIS和DIT（P <0.0001，除了第二次发作的IgG指数：P = 0.016）。在多变量 Cox 模型 [aHR (95% CI)] 中，第二次发作的风险在 KFLC-5.9 [2.0 (0.9-4.3)，P = 0.068] 和 KFLC-6.6 [2.1 (1.1-4.2)，P = 0.035]。KFLC-5.9 [4.9 (2.5-9.6), P < 0.0001], 其次是 KFLC-6.6 [3.4 (1.9-6.3), P < 0.0001]。KFLC-5.9 和 KFLC-6.6 对于二次发作（70.5、71.1 和 67.8）以及 MRI DIS 和 DIT（85.7、85.1 和 81.0）的诊断准确率略高于 OB。KFLC 指数 5.9 和 6.6 在评估多发性硬化症风险和诊断准确性方面略优于 OB。