ArticleBiomolecules2022
Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements.
Article in Biomolecules, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 8 papers, 1 of them a synthesis that pooled it.
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Who cites it
8 citing papers in PubMed, 1 synthesis or guideline pooled it, 12 citations in OpenAlex.
- The Use of Kappa Free Light Chains to Diagnose Multiple Sclerosis.Medicina (Kaunas, Lithuania) · 2022Pooled it
- Diagnostic Value of the Kappa Free Light Chain Index to Distinguish MOGAD, NMOSD, and MS.Neurology · 2026Article
- Diagnostic value of the kappa free light chain index in multiple sclerosis under the 2024 CSF positivity criterion: a multicentre study in oligoclonal band-negative patients.Frontiers in immunology · 2026Article
- Performance and comparison of FLCCheck: a novel serum free light chain assay for the Auxiliary Diagnosis of Multiple Myeloma.European journal of medical research · 2025Article
- The Kappa Free Light Chains Index and Central Vein Sign: Two New Biomarkers for Multiple Sclerosis Diagnosis.Neurology and therapy · 2025Review
- Elevated Kappa Index in the Absence of Cerebrospinal Fluid IgG Oligoclonal Bands: Contribution of Intrathecal IgM and IgA Synthesis.Biomolecules · 2025Article
- Laboratory Diagnosis of Intrathecal Synthesis of Immunoglobulins: A Review about the Contribution of OCBs and K-index.International journal of molecular sciences · 2024Review
- Inter-assay diagnostic accuracy of cerebrospinal fluid kappa free light chains for the diagnosis of multiple sclerosis.Frontiers in immunology · 2024Article
Corrections and comments
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Authors and funding
23 authors at 11 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The kappa index (K-Index), calculated by dividing the cerebrospinal fluid (CSF)/serum kappa free light chain (KFLC) ratio by the CSF/serum albumin ratio, is gaining increasing interest as a marker of intrathecal immunoglobulin synthesis. However, data on inter-laboratory agreement of these measures is lacking. The aim was to assess the concordance of CSF and serum KFLC measurements, and of K-index values, across different laboratories. KFLC and albumin of 15 paired CSF and serum samples were analyzed by eight participating laboratories. Four centers used Binding Site instruments and assays (B), three used Siemens instruments and assays (S), and one center used a Siemens instrument with a Binding Site assay (mixed). Absolute individual agreement was calculated using a two-way mixed effects intraclass correlation coefficient (ICC). Cohen's kappa coefficient (k) was used to measure agreement on positive (≥5.8) K-index values. There was an excellent agreement in CSF KFLC measurements across all laboratories (ICC (95% confidence interval): 0.93 (0.87-0.97)) and of serum KFLC across B and S laboratories (ICC: 0.91 (0.73-0.97)), while ICC decreased (to 0.81 (0.53-0.93)) when including the mixed laboratory in the analysis. Concordance for a positive K-Index was substantial across all laboratories (k = 0.77) and within S laboratories (k = 0.71), and very good (k = 0.89) within B laboratories, meaning that patients rarely get discordant results on K-index positivity notwithstanding the testing in different laboratories and the use of different platforms/assays.
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