Cerebrospinal fluid (CSF) kappa free light chain (KFLC) index has been described as a reliable marker of intrathecal IgG synthesis to diagnose multiple sclerosis (MS). Our aims were: (1) to compare the efficiency of KFLC through different interpretation approaches in diagnosing MS. (2) to evaluate the prognostic value of KFLC in radiologically and clinically isolated syndromes (RIS-CIS). We enrolled 133 MS patients and 240 with other neurological diseases (93 inflammatory including 18 RIS-CIS, 147 non-inflammatory). Albumin, lambda free light chain (LFLC) and KFLC were measured in the CSF and serum by nephelometry. We included two groups of markers: (a) corrected for blood-CSF barrier permeability: immunoglobulin G (IgG), KFLC and LFLC indexes. (b) CSF ratios (not including albumin and serum-correction): CSF KFLC/LFLC, CSF KFLC/IgG, CSF LFLC/IgG. KFLC were significantly higher in MS patients compared to those with other diseases (both inflammatory or not). KFLC index and CSF KFLC/IgG ratio showed high sensitivity (93% and 86.5%) and moderate specificity (85% and 88%) in diagnosing MS. RIS-CIS patients who converted to MS showed greater KFLC index and CSF KFLC/IgG. Despite OB are confirmed to be the gold-standard to detect intrathecal IgG synthesis, the KFLC confirmed their accuracy in MS diagnosis. A “kappa-oriented” response characterizes MS and has a prognostic impact in the RIS-CIS population.

脑脊液（CSF）κ自由轻链（KFLC）指数已被描述为鞘内IgG合成诊断多发性硬化症（MS）的可靠标记。我们的目标是：（1）通过不同的解释方法比较KFLC在诊断MS中的效率。（2）评估KFLC在放射学和临床孤立综合征（RIS-CIS）中的预后价值。我们招募了133例MS患者和240例其他神经系统疾病（93例炎症，包括18例RIS-CIS，147例非炎症）。通过比浊法在CSF和血清中测量白蛋白，λ自由轻链（LFLC）和KFLC。我们包括两组标记物：（a）校正了血脑脊液屏障通透性：免疫球蛋白G（IgG），KFLC和LFLC指数。（b）脑脊液比率（不包括白蛋白和血清校正）：脑脊液KFLC / LFLC，脑脊液KFLC / IgG，脑脊液LFLC / IgG。与患有其他疾病（无论是否发炎）的MS患者相比，MS患者的KFLC显着更高。KFLC指数和CSF KFLC / IgG比值在诊断MS中显示出高灵敏度（93％和86.5％）和中度特异性（85％和88％）。转换为MS的RIS-CIS患者表现出更高的KFLC指数和CSF KFLC / IgG。尽管OB被证实是检测鞘内IgG合成的金标准，但KFLC证实了它们在MS诊断中的准确性。MS的特征是“以κ为导向”，对RIS-CIS人群有预后影响。转换为MS的RIS-CIS患者表现出更高的KFLC指数和CSF KFLC / IgG。尽管OB被证实是检测鞘内IgG合成的金标准，但KFLC证实了它们在MS诊断中的准确性。MS的特征是“以κ为导向”，对RIS-CIS人群具有预后影响。转换为MS的RIS-CIS患者表现出更高的KFLC指数和CSF KFLC / IgG。尽管OB被证实是检测鞘内IgG合成的金标准，但KFLC证实了它们在MS诊断中的准确性。MS的特征是“以κ为导向”，对RIS-CIS人群有预后影响。