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.
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。