Abstract：
BACKGROUND: Free light chain (FLC) measurements are important in diagnosing monoclonal gammopathies. As FLC are heterogeneous, different reagents and instruments for measuring FLC concentrations may give diverging results that affect assessment of patients with monoclonal gammopathies. Here we investigated agreement between different FLC methods using data from the Swedish external quality assurance (EQA) programme.
METHODS: The two main FLC assays, N Latex FLC (Siemens) and Serum Freelite (The Binding Site), using four nephelometric or turbidimetric instrument platforms, were compared. Results from 27 EQA rounds distributed to 11-16 Swedish hospital laboratories during 2015-2020 were investigated.
RESULTS: The kappa (κ) FLC measurements deviated significantly over time, but when only nephelometry was used, deviation from the mean was lower (median ranges: -5% to 13 %). The CV was significantly higher for the Freelite assay (mean CV = 8.7) than for the N latex assay (mean CV = 5.7) (p < 0.0001). The coefficient of determination between all combinations of reagents and instrument platforms used was generally good (r2 = 0.76-0.87), and the correlation slope acceptable (0.81-1.2). For lambda (λ) FLC measurements, no concordance between combinations of instruments and reagents is apparent, deviating between -40 % to + 48 % from the mean. The CV was significantly higher for the combination with nephelometry and the Freelite assay (CV mean = 13.9 %) than nephelometry and the N latex assay (CV mean = 9.9 %) (p <0.001). The coefficient of determination varied between combinations of reagents and instrument platforms (r2 = 0.59-0.89) and the slope ranged between 0.48 and 1.5. Significant differences between the two reagents used were sometimes noted.
CONCLUSIONS: Imprecision in λFLC affects the κFLC/λFLC ratio. This may be important in clinical assessment of patients, especially differentiating between monoclonal and polyclonal gammopathies.
METHODS: The two main FLC assays, N Latex FLC (Siemens) and Serum Freelite (The Binding Site), using four nephelometric or turbidimetric instrument platforms, were compared. Results from 27 EQA rounds distributed to 11-16 Swedish hospital laboratories during 2015-2020 were investigated.
RESULTS: The kappa (κ) FLC measurements deviated significantly over time, but when only nephelometry was used, deviation from the mean was lower (median ranges: -5% to 13 %). The CV was significantly higher for the Freelite assay (mean CV = 8.7) than for the N latex assay (mean CV = 5.7) (p < 0.0001). The coefficient of determination between all combinations of reagents and instrument platforms used was generally good (r2 = 0.76-0.87), and the correlation slope acceptable (0.81-1.2). For lambda (λ) FLC measurements, no concordance between combinations of instruments and reagents is apparent, deviating between -40 % to + 48 % from the mean. The CV was significantly higher for the combination with nephelometry and the Freelite assay (CV mean = 13.9 %) than nephelometry and the N latex assay (CV mean = 9.9 %) (p <0.001). The coefficient of determination varied between combinations of reagents and instrument platforms (r2 = 0.59-0.89) and the slope ranged between 0.48 and 1.5. Significant differences between the two reagents used were sometimes noted.
CONCLUSIONS: Imprecision in λFLC affects the κFLC/λFLC ratio. This may be important in clinical assessment of patients, especially differentiating between monoclonal and polyclonal gammopathies.
摘要：
背景：游离轻链（FLC）测量在诊断单克隆丙种球蛋白病中很重要。由于FLC是异构的，用于测量FLC浓度的不同试剂和仪器可能会产生不同的结果,从而影响对单克隆免疫球蛋白病患者的评估.在这里，我们使用瑞典外部质量保证（EQA）计划的数据调查了不同FLC方法之间的一致性。
方法：两种主要的FLC测定法，N胶乳FLC（西门子）和血清弗氏（结合位点），使用四个比浊法或比浊法仪器平台，进行了比较。调查了2015-2020年期间分发给11-16个瑞典医院实验室的27个EQA回合的结果。
结果：随着时间的推移，κ(κ)FLC测量值显著偏离，但是当只使用比浊法时，与平均值的偏差较低(中位数范围:-5%~13%).Freelite测定(平均CV=8.7)的CV显著高于N胶乳测定(平均CV=5.7)(p<0.0001)。使用的所有试剂和仪器平台组合之间的测定系数总体良好（r2=0.76-0.87），和相关斜率可接受(0.81-1.2)。对于lambda(λ)FLC测量，仪器和试剂的组合之间没有明显的一致性，偏离平均值-40%至+48%。与比浊法和Freelite测定(CV平均值=13.9%)组合的CV显著高于比浊法和N胶乳测定(CV平均值=9.9%)(p<0.001)。测定系数在试剂和仪器平台的组合之间变化(r2=0.59-0.89),并且斜率在0.48和1.5之间。有时注意到使用的两种试剂之间的显著差异。
结论：λFLC的不精确性影响κFLC/λFLC比值。这在患者的临床评估中可能很重要，尤其是区分单克隆和多克隆丙种球蛋白。
方法：两种主要的FLC测定法，N胶乳FLC（西门子）和血清弗氏（结合位点），使用四个比浊法或比浊法仪器平台，进行了比较。调查了2015-2020年期间分发给11-16个瑞典医院实验室的27个EQA回合的结果。
结果：随着时间的推移，κ(κ)FLC测量值显著偏离，但是当只使用比浊法时，与平均值的偏差较低(中位数范围:-5%~13%).Freelite测定(平均CV=8.7)的CV显著高于N胶乳测定(平均CV=5.7)(p<0.0001)。使用的所有试剂和仪器平台组合之间的测定系数总体良好（r2=0.76-0.87），和相关斜率可接受(0.81-1.2)。对于lambda(λ)FLC测量，仪器和试剂的组合之间没有明显的一致性，偏离平均值-40%至+48%。与比浊法和Freelite测定(CV平均值=13.9%)组合的CV显著高于比浊法和N胶乳测定(CV平均值=9.9%)(p<0.001)。测定系数在试剂和仪器平台的组合之间变化(r2=0.59-0.89),并且斜率在0.48和1.5之间。有时注意到使用的两种试剂之间的显著差异。
结论：λFLC的不精确性影响κFLC/λFLC比值。这在患者的临床评估中可能很重要，尤其是区分单克隆和多克隆丙种球蛋白。
