Academic Journal
Free light chain EQA: Analytical variability with clinical consequences - Data from 25 Italian EQA exercises (2021-2025).
| Τίτλος: | Free light chain EQA: Analytical variability with clinical consequences - Data from 25 Italian EQA exercises (2021-2025). |
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| Συγγραφείς: | Pasotti F; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Da Molin S; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Bosoni T; Laboratory of Clinical Analysis, IRCCS Policlinico San Matteo, Pavia, Italy., Azzarà G; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Liga G; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Moriello G; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Zaccaria B; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy., Buoro S; Regional Coordination Center for Laboratory Medicine of Lombardy Region, Milan, Italy. |
| Πηγή: | Clinica chimica acta; international journal of clinical chemistry [Clin Chim Acta] 2026 Aug 15; Vol. 590, pp. 121056. Date of Electronic Publication: 2026 May 05. |
| Τύπος έκδοσης: | Journal Article |
| Γλώσσα: | English |
| Στοιχεία περιοδικού: | Publisher: Elsevier Country of Publication: Netherlands NLM ID: 1302422 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1873-3492 (Electronic) Linking ISSN: 00098981 NLM ISO Abbreviation: Clin Chim Acta Subsets: MEDLINE |
| Imprint Name(s): | Original Publication: Amsterdam, Elsevier. |
| Ιατρικοί όροι (MeSH): | Immunoglobulin Light Chains*/blood , Immunoglobulin kappa-Chains*/blood , Immunoglobulin lambda-Chains*/blood, Paraproteinemias/diagnosis ; Paraproteinemias/blood ; Humans ; Italy ; Quality Control |
| Περίληψη: | Serum free light chains (FLC) κ and λ, and the κ/λ ratio, are key biomarkers for the diagnosis, risk stratification and monitoring of monoclonal gammopathies. However, substantial between-method variability still limits harmonised interpretation. We analysed five years of external quality assessment (EQA) data from an Italian FLC scheme. Twenty-five EQA rounds (2021-2025) yielded 2218 results: 746 for κ FLC, 746 for λ FLC and 726 for the κ/λ ratio. Data were processed according to ISO 13528 using robust statistics and method-specific peer groups. Inter-laboratory precision within homogeneous peer groups was generally acceptable, with typical coefficients of variation around 10-20% for κ and λ FLC. By contrast, marked between-method differences were observed. Compared with Siemens N Latex, Binding Site Freelite assays yielded approximately two-fold higher mean κ FLC concentrations (relative mean bias ≈ +94%) and lower mean λ FLC concentrations (relative mean bias ≈ -82%), leading to substantial discrepancies in κ/λ ratio interpretation. Stratified analysis across low, intermediate and high concentration bands showed that the positive κ bias of Freelite persisted throughout the analytical range, whereas the global negative λ bias was largely driven by a subset of high-concentration samples with very high N Latex values. Bland-Altman analysis confirmed wide limits of agreement for both analytes. These findings indicate that current FLC assays are not interchangeable and that κ/λ ratios should not be interpreted using universal reference intervals. Method-specific cut-offs, method-consistent follow-up and method-stratified EQA schemes are required pending international standardization of FLC measurement. (Copyright © 2026 Elsevier B.V. All rights reserved.) |
| Competing Interests: | Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. |
| Contributed Indexing: | Keywords: External quality assessment; Free light chains; Laboratory harmonisation; Method comparison; κ/λ ratio |
| Substance Nomenclature: | 0 (Immunoglobulin Light Chains) 0 (Immunoglobulin kappa-Chains) 0 (Immunoglobulin lambda-Chains) |
| Entry Date(s): | Date Created: 20260507 Date Completed: 20260710 Latest Revision: 20260710 |
| Update Code: | 20260711 |
| DOI: | 10.1016/j.cca.2026.121056 |
| PMID: | 42097195 |
| Βάση Δεδομένων: | MEDLINE |
| ISSN: | 1873-3492 |
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| DOI: | 10.1016/j.cca.2026.121056 |