Konen Franz F, Schwenkenbecher Philipp, Wurster Ulrich, Jendretzky Konstantin F, Möhn Nora, Gingele Stefan, Sühs Kurt-Wolfram, Hannich Malte J, Grothe Matthias, Witte Torsten, Stangel Martin, Süße Marie, Skripuletz Thomas
Department of Neurology, Hannover Medical School, Hannover, Germany.
Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Greifswald, Germany.
J Cent Nerv Syst Dis. 2021 Nov 19;13:11795735211042166. doi: 10.1177/11795735211042166. eCollection 2021.
The determination of kappa free light chains (KFLC) in cerebrospinal fluid (CSF) is an upcoming biomarker for the detection of an intrathecal immunoglobulin synthesis. Since renal function impairment leads to altered serum KFLC and albumin concentrations, interpretation of KFLC in CSF may be influenced by these parameters.
In this two-center study, the influence of renal function (according to the CKD-EPI creatinine equation) on KFLC and albumin concentrations was investigated in patients with "physiological" (n = 139), "non-inflammatory" (n = 146), and "inflammatory" (n = 172) CSF profiles in respect to the KFLC index and the evaluation in quotient diagrams in reference to the hyperbolic reference range (KFLC IF).
All sample groups displayed declining KFLC indices and KFLC IF values with decreasing renal function (-values between <.0001 and .0209). In "inflammatory" CSF profile samples, 15% of the patients presented a KFLC index <5.9 while 10% showed an intrathecal KFLC fraction below Q(lim), suggesting possible false negative KFLC results.
The influence of renal function should be considered while interpreting KFLC results in patients with neuroinflammatory diseases. The interpretation of KFLC in quotient diagrams is less susceptible to renal function impairment than the KFLC index and should be preferentially used.
脑脊液（CSF）中游离κ轻链（KFLC）的测定是一种用于检测鞘内免疫球蛋白合成的新兴生物标志物。由于肾功能损害会导致血清KFLC和白蛋白浓度发生变化，脑脊液中KFLC的解读可能会受到这些参数的影响。
在这项双中心研究中，针对“生理性”（n = 139）、“非炎性”（n = 146）和“炎性”（n = 172）脑脊液谱的患者，根据CKD-EPI肌酐方程研究肾功能对KFLC和白蛋白浓度的影响，涉及KFLC指数以及参照双曲线参考范围（KFLC IF）在商图中的评估。
所有样本组的KFLC指数和KFLC IF值均随肾功能下降而降低（P值在<.0001至.0209之间）。在“炎性”脑脊液谱样本中，15%的患者KFLC指数<5.9，而10%的患者鞘内KFLC分数低于Q(lim)，提示可能出现KFLC结果假阴性。
在解读神经炎性疾病患者的KFLC结果时应考虑肾功能的影响。与KFLC指数相比，商图中KFLC的解读受肾功能损害的影响较小，应优先使用。
