Method comparison of three serum free light chain assays on the Roche Cobas 6000 c501 chemistry analyzer

• Published in: Clinical chemistry and laboratory medicine Vol. 60; no. 3; pp. 379 - 385
• Main Authors: Augustijn, Dieuwertje, Jacobs, Joannes F.M., Russcher, Henk
• Format: Journal Article
• Language: English
• Published: Germany De Gruyter 23.02.2022; Walter De Gruyter & Company
• Subjects: Assaying; Binding sites; Biological Assay; Chains; free light chains; Humans; Immunoglobulin kappa-Chains; Immunoglobulin lambda-Chains; Immunoglobulin Light Chains; Laboratories; Light chains; M-protein; Monoclonal gammopathy; Multiple Myeloma; Paraproteinemias - diagnosis; Research Design; multiple myeloma; free light chains; M-protein; monoclonal gammopathy
• ISSN: 1434-6621; 1437-4331
• DOI: 10.1515/cclm-2021-1029

Free light chains (FLC) are important in the diagnosis, prognosis and monitoring of therapy response of patients with monoclonal gammopathies. In this study, we performed a method comparison of three FLC assays on the Cobas 6000 c501 chemistry analyzer of Roche Diagnostics. Samples of 119 patients with various monoclonal gammopathies and 26 control patients were measured with the Freelite (The Binding Site), Diazyme (Diazyme Laboratories) and KLoneus (Trimero Diagnostics) FLC assays. A method comparison was performed and reference intervals of the three assays were validated. The analysis of the Bland-Altman agreement showed bias between the three FLC assays, ranging from -62.7 to 5.1% for FLC and between -29.2 to 80.5% for FLC. The Freelite and Diazyme assays have the highest agreement. The concordance of the FLC-ratio ranges from 41 to 75%, with the highest concordance between the Freelite and KLoneus assays. The FLC-ratio in 25 sera from healthy controls were within the reference ranges of the Freelite and KLoneus assays. The FLC-ratio was elevated in all 25 samples tested with the Diazyme assay. The agreement for the free light chains is highest between the Freelite and the Diazyme assay and fair for the KLoneus assay. However, concordance of the FLC-ratio is highest when the Freelite and KLoneus assays were compared. Our data suggest that concordance for the Diazyme assay could be improved by recalibration. Because of absolute differences between the three methods in individual patients, none of the three FLC assays can be used interchangeably.