Assessment of the analytical performance and the sensitivity of serum free light chains immunoassay in patients with monoclonal gammopathy.
OBJECTIVE
A new immunoassay which quantifies Kappa, Lambda free light chains (FLC) and a ratio of Kappa to Lambda FLC has been reported to be sensitive for detecting a variety of FLC diseases. We assessed the analytical criteria and the diagnostic performance of this immunoassay in patients who present a monoclonal gammopathy.


METHODS
Quantification of FLC, serum protein electrophoresis (SPE) and immunofixation (IFE) were performed on patients who present a monoclonal gammopathy of undetermined significance (MGUS), an intact immunoglobulin multiple myeloma (IIMM) or a light chain multiple myeloma (LCMM).


RESULTS
The monoclonal component was identified by IFE in the sera of all patients. Based on the diagnostic reference range, the ratio of Kappa to Lambda FLC was abnormal in 25% of the tested population, compared to 94% for SPE in MGUS patients. For IIMM and LCMM, the FLC ratio was abnormal in 70% and 100% of the population, compared to 85% and 40% for SPE, respectively.


CONCLUSIONS
SPE and IFE have a higher sensitivity for identifying MGUS and IIMM.
Wolff
Fleur
F
Laboratory of Clinical Chemistry, CHU Brugmann, Place Van Gehuchten 4, 1020 Brussels, Belgium. fleur.wolff@chu-brugmann.be
Thiry
Claire
C
Willems
Dominique
D
D000328:Adult; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007145:Immunoglobulin kappa-Chains / Q000097:blood*; D007146:Immunoglobulin lambda-Chains / Q000097:blood*; D007136:Immunoglobulins / Q000097:blood; D008297:Male; D008875:Middle Aged; D010265:Paraproteinemias / Q000097:blood* / Q000175:diagnosis / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D007136:Immunoglobulins