Overestimation of free light chain antigen excess rate

Clinica Chimica Acta; International Journal of Clinical Chemistry
Martine VercammenXavier Bossuyt

Abstract

Free light chains (FLC) are useful biomarkers for diagnosis and follow-up of plasma cell disorders. FLC quantification is encumbered by non-linearity and antigen excess (>4-fold difference between results obtained at the 2000- and 100-fold dilution). FLC concentration was measured with Freelite® reagents on the BNII, using 100- and 2000-fold dilutions in 3645 samples. Samples displaying antigen excess were re-measured at the 2000- and/or 400-fold dilution. Carryover was evaluated by tracing samples to cuvettes and by measuring a normal sample in cuvettes that previously contained samples with a high FLC concentration. Antigen excess occurred in 0.93% of samples for κ and in 0.55% of samples for λ. In 81.5% of the cases, it could not be confirmed by a re-analysis of a 2000-fold and/or a 400-fold diluted sample. Real antigen excess was documented in 0.25% and 0.03% of the samples for κ and λ FLC, respectively. In the low concentration range (2000-fold dilution), imprecision was high. False antigen excess was reduced by batch analysis, introducing cleaning and rinsing procedures and using the 400-fold dilution. No antigen excess was detected in samples with normal FLC concentrations. Falsely high results occur by imprecision in th...Continue Reading

References

Jul 16, 2010·Clinical Chemistry and Laboratory Medicine : CCLM·Markus BosmannUdo Steigerwald
Jul 12, 2011·Clinica Chimica Acta; International Journal of Clinical Chemistry·Martine VercammenXavier Bossuyt
Jan 31, 2012·Clinica Chimica Acta; International Journal of Clinical Chemistry·Ellen JennerStephen Harding
Feb 3, 2012·Journal of Autoimmunity·Pilar Brito-ZerónManuel Ramos-Casals
Sep 13, 2014·Hematology/oncology Clinics of North America·Robert A KyleS Vincent Rajkumar

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Citations

Jun 3, 2017·American Journal of Clinical Pathology·Anne-Sophie MessiaenDieter De Smet
Oct 16, 2019·Critical Reviews in Clinical Laboratory Sciences·Laura CaponiMaria Franzini

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