Objectives: Free light chain (FLC) measurement gained a lot of interest for diagnostic workup of monoclonal gammopathy.
Methods: We evaluated the performance of turbidimetric polyclonal Freelite (The Binding Site, Birmingham, UK) assays on Cobas 6000 (Roche Diagnostics, Rotkreuz, Switzerland) and nephelometric monoclonal N Latex (Siemens Healthcare Diagnostics, Marburg, Germany) assays on BN ProSpec (Dade Behring, Deerfield, IL) vs established nephelometric Freelite assays on BN ProSpec.
Results: Analytical performance was acceptable. Method comparison (n = 118) showed significant proportional FLC differences for N Latex assays. However, good correlation and clinical concordance were shown. Recovery study in the low concentration range demonstrated consistent over- and underrecovery for Freelite reagents, hampering future research on prognostic value of suppressed noninvolved FLC. Antigen excess detection was successful for κ FLC in three-fourths of cases with Freelite reagents and in all cases with N Latex reagents. However, the latter resulted in underestimated κ FLC concentrations.
Conclusions: FLC analysis requires continuous awareness of analytical limitations. Monitoring of disease response requires FLC analysis on the same platform using the same reagents.
Keywords: Free light chains; Monoclonal; Monoclonal gammopathy; Myeloma; Nephelometry; Polyclonal; Turbidimetry.
© American Society for Clinical Pathology, 2017. All rights reserved. For permissions, please e-mail: [email protected]