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Open Access Published by De Gruyter June 11, 2011

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

Henk te Velthuis, Ingrid Knop, Peter Stam, Monic van den Broek, Hannie Klaasse Bos, Suzanne Hol, Elisa Teunissen, Karin Schulte Fischedick, Harald Althaus, Brigitta Schmidt, Carola Wagner and Roel Melsert


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.

Corresponding author: Dr. Henk te Velthuis, Department of R&D, Sanquin Reagents, Plesmanlaan 125, 1066CX Amsterdam, The Netherlands Phone: +31 20 512 3665, Fax: +31 20 512 3170

Received: 2011-03-03
Accepted: 2011-03-22
Published Online: 2011-06-11
Published in Print: 2011-08-01

©2011 by Walter de Gruyter Berlin Boston

This content is open access.

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