Serum Free Light Chain Assay: Shift Toward a Higher κ/λ Ratio.

Rindlisbacher, Barbara; Schild, Christof; Egger, Florence; Bacher, Vera U.; Pabst, Thomas; Leichtle, Alexander; Andres, Martin; Sédille-Mostafaie, Nazanin (2020). Serum Free Light Chain Assay: Shift Toward a Higher κ/λ Ratio. The journal of applied laboratory medicine, 5(1), pp. 114-125. Oxford University Press 10.1093/jalm.2019.029330

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BACKGROUND

The analysis of serum free light chains (FLCs) is clinically relevant for the diagnosis and therapeutic management of clonal plasma cell disorders. This study compares the performance of monoclonal and polyclonal FLC κ and λ assays in clinical samples determined in a single academic center.

METHODS

Serum FLCs were analyzed from 102 patients using the Freelite (Binding Site) and N Latex (Siemens) assays on the BN ProSpec System (Siemens). When available, data for protein electrophoresis, immunofixation, C-reactive protein, and estimated glomerular filtration rate (eGFR) were combined with FLC results to evaluate performance.

RESULTS

Method evaluation showed acceptable imprecision and inaccuracy measures of <4.4% and 12.9%, respectively. Poor agreement between the methods was observed, including constant and proportional bias and poor correlation (Kendall τ, 0.671-0.901). The N Latex assay was not affected by the renal impairment estimated by eGFR, unlike the FLC κ/λ ratio results by the Freelite assay. With the Freelite assay, 98% of putative controls without monoclonal gammopathy (n = 42) showed a κ/λ ratio that was above the median of the standard diagnostic range or renal diagnostic range. A shift toward higher κ/λ ratios was also observed when retrospective data between 2011 and 2017 were compared.

CONCLUSIONS

Unlike the Freelite assay, κ/λ ratios analyzed with the N Latex assay were not affected by renal failure. Both methods showed acceptable performances using nephelometry, but they were poorly correlated. A shift toward κ/λ ratios might impair the specificity of borderline increased κ/λ results. This should be considered when interpreting FLC κ and λ results.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Institute of Clinical Chemistry 04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Haematology and Central Haematological Laboratory 04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Medical Oncology
UniBE Contributor:	Schild, Christof, Bacher, Vera Ulrike, Pabst, Thomas Niklaus, Leichtle, Alexander Benedikt (B), Andres, Martin, Sédille-Mostafaie, Nazanin
Subjects:	600 Technology > 610 Medicine & health
ISSN:	2475-7241
Publisher:	Oxford University Press
Language:	English
Submitter:	Pierrette Durand Lüthi
Date Deposited:	30 Jun 2020 15:16
Last Modified:	02 Mar 2023 23:33
Publisher DOI:	10.1093/jalm.2019.029330
PubMed ID:	32445339
URI:	https://boris.unibe.ch/id/eprint/144481