N Latex FLC – new monoclonal high-performance assays for the determination of free light chain kappa and lambda

Abstract

Background: High serum concentrations of monoclonal free light chain (FLC) kappa or lambda are markers of plasma cell dyscrasia. Methods: We developed new, latex-enhanced, specific nephelometric assays based on monoclonal antibodies for the determination of FLC kappa and lambda in serum, EDTA plasma and Li-heparin plasma for use on the Siemens BN systems. Results: Reference ranges were determined from 369 samples: FLC kappa 6.7-22.4 mg/L, FLC lambda 8.3-27.0 mg/L and kappa/lambda ratio 0.31-1.56. Protection from falsely low results due to antigen excess is obtained with a built-in pre-reaction in the assay protocols. Lot-to-lot consistency between three different lots of reagent, calibrators and supplementary reagent lots showed normalized differences -7.5%. The reproducibility of serum samples varied between 4% and 7%. The method comparison with Freelite assays showed normalized differences of 19.7%, 32.7% and 21.7%, respectively, for FLC kappa, lambda and ratio, correlations of 0.94, 0.77 and 0.73, and concordance rates of 99.2%, 94.2% and 95%. Conclusions: N Latex FLC demonstrates high precision, good lot-to-lot consistency and freedom from a high-dose hook effect. The method comparison between Freelite and the N Latex FLC assays showed good clinical concordance. Further studies need to reveal the clinical value of the new FLC assays.

Biochemical markers in early diagnosis and management of systemic amyloidoses

“…It is important to note that all these studies were performed using the Freelite immuno-nephelometric assay (The Binding Site), based on the use of polyclonal anti-FLC antibodies [94]. More recently, a novel assay for FLC quantification (N latex FLC, Siemens) based on monoclonals, has been developed and introduced on the market [95]. The performance of the two assays for FLC quantification in AL amyloidosis patients has recently been compared [96,97].…”

Evaluation of the N Latex free light chain assay in the diagnosis and monitoring of AL amyloidosis

“…Recently, serum κ and λ FLC immunonephelometric assays based on monoclonal antibodies have become commercially available (N Latex FLC assay, Siemens) [13]. This new FLC assay appears to have some analytical advantages over the Freelite ™ assay [14] but lacks clinical validation, particularly in AL amyloidosis where FLC measurement has such a central and critical role in patient management.…”

Clinical comparison of new monoclonal antibody-based nephelometric assays for free light chain kappa and lambda to polyclonal antibody-based assays and immunofixation electrophoresis

“…Recently, new monoclonal antibody-based nephelometric N Latex FLC assays for the Siemens BN ™ systems were developed with good performance characteristics (10) . The N Latex FLC assays showed good batchto-batch reproducibility, antigen excess security and high precision.…”