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. 2024 Dec 12;272(1):30.
doi: 10.1007/s00415-024-12826-y.

Kappa index for multiple sclerosis diagnosis: an accurate biomarker of intrathecal synthesis

Domizia Vecchio #  1 , C Puricelli #  2 , E Virgilio  3 , F Passarelli  2 , S Guida  2 , P Naldi  3 , I Crespi  2 , U Dianzani  2 , C Comi  3
Affiliations

Kappa index for multiple sclerosis diagnosis: an accurate biomarker of intrathecal synthesis

Domizia Vecchio et al. J Neurol. .

Abstract

Background: Cerebrospinal fluid (CSF) kappa-free light chains (KFLC) are becoming a diagnostic biomarker for multiple sclerosis (MS).

Objectives: We aimed to compare the diagnostic performance of intrathecal synthesis biomarkers to that of oligoclonal bands (OB) in diagnosing MS, radiological and clinical isolated syndromes (RIS-CIS) on a large cohort of patients collected over 10 years.

Methods: We collected 1124 patients (58% females) in 10 years who underwent CSF analysis for intrathecal synthesis in the diagnostic work-up, and they were classified according to their diagnosis as 417 MS, 287 with other neurological inflammatory disorders (including 76 RIS-CIS), and 420 non-inflammatory diseases (excluding lymphoproliferative and infective diagnosis).

Results: MS patients significantly differ from all other groups (including if considering the RIS-CIS cohort) for CSF KFLC, KFLC intrathecal fraction (IF), Kappa index, and OB. Evaluating the diagnostic performance, the Kappa index cut-off was 6.4 for diagnosing MS and 5.7 for predicting OB. A diagnostic algorithm could avoid IEF if the Kappa index is higher than 20.

Conclusions: The KFLC index confirmed its accuracy for MS diagnosis in this large Italian cohort, adding information also in the RIS-CIS population.

Keywords: Intrathecal synthesis; Kappa free light chains; Kappa index.

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Conflict of interest statement

Declarations. Conflicts of interest: None for all authors for this work. Ethics approval: Local Ethical Committee approvals (Comitato Etico Interaziendale AOU “Maggiore della Carità” di Novara, ASL BI, ASL NO, ASL VCO): CE 060/2022 and 260/2022). Consent to participate/consent for publication: written consent obtained from all participants.

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