Quantitative serum free light chain assay: Analytical issues

Tate, Jill, Bazeley, Sheree, Sykes, Stephen and Mollee, Peter (2009) Quantitative serum free light chain assay: Analytical issues. Clinical Biochemist Reviews, 30 3: 131-140.

Author Tate, Jill
Bazeley, Sheree
Sykes, Stephen
Mollee, Peter
Title Quantitative serum free light chain assay: Analytical issues
Journal name Clinical Biochemist Reviews   Check publisher's open access policy
ISSN 0159-8090
Publication date 2009-08
Sub-type Article (original research)
Volume 30
Issue 3
Start page 131
End page 140
Total pages 10
Editor Sam Vasikaran
Place of publication Mt. Lawley, WA, Australia
Publisher Australasian Association of Clinical Biochemists
Language eng
Subject 1103 Clinical Sciences
Formatted abstract
Serum free light chain (FLC) assay is an important advance in the diagnosis and monitoring of monoclonal light chain diseases and a complementary test to serum protein electrophoresis and immunofixation. Immunoturbidimetric and immunonephelometric assays for serum FLC are available on routine chemistry analysers and can detect FLC down to ∼1 mg/L. These assays use polyclonal anti-human FLC antisera and require acceptable imprecision, specificity, accuracy, and reproducibility between reagent batches to prevent under- or over-estimation of FLC concentration.

Assay imprecision determined between reagent lots has a variation of 8-45% for FLC concentrations and 17-32% for the calculated κ/λ FLC ratio. Dilution studies indicate some over-recovery of FLC, which may depend upon the dilution matrix. However, greater discrepancies are underestimation from nonlinear reactions and overestimation possibly from interferences or multi-reactivity to polymeric FLC. Nonlinear monoclonal FLC give concentrations which are 2- to 6-fold increased at higher sample dilution and FLC measured on different platforms may not give the same results.

Laboratory staff and clinicians should be aware of the analytical limitations of the FLC assay. Assay imprecision, especially with different lots of FLC reagent, may have a significant effect on changes in the FLC concentration and κ/λ FLC ratio. Sample dilution anomalies have the potential to confound result interpretation for patients with monoclonal light chain disease. These issues, if not adequately appreciated, have the potential to mislead clinical diagnosis and assessment of response to therapy.
Keyword Clinical diagnosis
Serum free light chain (FLC)
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Published under "Commentary".

Document type: Journal Article
Sub-type: Article (original research)
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Created: Mon, 27 Sep 2010, 09:53:58 EST by Ms May Balasaize on behalf of Faculty Of Health Sciences