Consistency and correlation of a domestic Kehua serum free light chain assay with two imported analytical systems
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Published on: July 14, 2023
Yansong Ren1, Shoulei Wang1, Limin Han2
1State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China.
Background:
Serum free light chain (sFLC) testing is central to the diagnosis and monitoring of plasma cell disorders, but assay availability and implementation can vary by laboratory setting. We evaluated a domestic latex-enhanced immunoturbidimetric Kehua serum sFLC assay against Freelite and N Latex systems.
Methods:
Residual serum samples from 133 adults with suspected or established monoclonal gammopathies were measured in parallel by Kehua and Freelite; 122 were also tested by N Latex. Precision was assessed with low- and high-level serum controls. Method agreement was evaluated using correlation, Passing-Bablok regression, Bland-Altman analysis, qualitative concordance and comparator-defined ROC analysis.
Results:
Kehua within-run CVs were <5% for κ and λ controls. Agreement with Freelite was excellent for FLC-κ, FLC-λ and κ/λ ratio (Pearson r = 0.988-1.000; CCC = 0.983-0.999), with Passing-Bablok slopes close to unity. Agreement with N Latex was also strong (r = 0.991-0.998), although κ/λ ratio showed proportional bias. Total qualitative concordance was 89.47-93.23% versus Freelite and 83.61-91.80% versus N Latex, with Cohen's κ of 0.67-0.85. Comparator-defined ROC AUCs were 0.994-0.999 for elevated FLC-κ or FLC-λ and 0.796-0.869 for κ/λ ratio abnormality.
Conclusion:
The Kehua serum assay demonstrated acceptable precision and good clinical agreement with two imported methods. It may serve as a domestic option for routine serum sFLC quantification, provided method-specific intervals are maintained and the same platform is used for serial monitoring.
