FLC polymerization: Another hurdle towards standardization of FLC measurements.

In the November issue of this journal, Caponi et al. convincingly show that free light chain (FLC) lambda measurements are influenced by the FLC-polymerization status. With liquid chromatography using a size-exclusion column they separated monoclonal FLC dimers from monomers. FLC analysis of these different fractions clearly indicated that Freelite (The Binding Site) reacted better with FLC dimers than with FLC monomers. In contrast, N Latex FLC (Siemens) recognizes mainly FLC monomers and has poor reactivity with the FLC dimers. This important finding may be one of the leading factors to explain discrepancies in FLC-quantification using Freelite versus other immunochemical assays such as N-Latex FLC.