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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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