ArticleNeurology(R) neuroimmunology & neuroinflammation2025
Diagnostic Utility of Kappa Free Light Chain Index in Adults With Inaugural Optic Neuritis.
Article in Neurology(R) neuroimmunology & neuroinflammation, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
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Who cites it
6 citing papers in PubMed.
- Intrathecal immunoglobulin production in the diagnosis, prognosis, and monitoring of autoimmune diseases of the central nervous system.Journal of translational autoimmunity · 2026Review
- Diagnostic Value of the Kappa Free Light Chain Index to Distinguish MOGAD, NMOSD, and MS.Neurology · 2026Article
- Kappa free light chain index in multiple sclerosis and other inflammatory CNS diseases: a pilot single-center study from Argentina.Frontiers in immunology · 2026Article
- Kappa index: real-world study for assessing cut-off values that provide the best accuracy for multiple sclerosis diagnosis in patients with CIS.Frontiers in immunology · 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
- Positive cerebrospinal fluid in the 2024 McDonald criteria for multiple sclerosis.EBioMedicine · 2025Review
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14 authors.
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Abstract
BACKGROUND AND
objectivesA simple, quick, and reproducible procedure for distinguishing multiple sclerosis (MS), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), and neuromyelitis optica spectrum disorder (NMOSD) at inaugural optic neuritis (ION) could be highly valuable in guiding early management.
methodsWe included all adults admitted to the MS center of Marseille for ION between March 2016 and April 2024, with CSF analysis including the kappa free light chain (K-FLC) index. Receiver operating characteristic curves were used to measure the diagnostic ability of the K-FLC index.
resultsTwo hundred twenty-seven adults were admitted for ION; 210 (93%) had a K-FLC index measurement. MS was diagnosed in 84 (40%); clinically isolated syndrome suggestive of MS in 77 (36.5%), including 20 with future conversion to MS (CISwc); MOGAD in 26 (12.5%); NMOSD in 13 (6%); and other inflammatory disorders in 10 (5%). A K-FLC index ≥6.7 differentiated MS/CISwc from other diagnoses with specificity 86% and sensitivity 95% (area under the curve [AUC] 0.94). A K-FLC index <4.9 differentiated MOGAD from other diagnoses with specificity 63% and sensitivity 92% (AUC 0.78) and MOGAD from MS/CISwc with specificity 96% and sensitivity 92% (AUC 0.97). Among all patients, 93 (44%) had a K-FLC index <4.9: 24 of these (26%) had MOGAD and 5 (5.5%) MS/CISwc. Among the remaining patients with a K-FLC index ≥4.9 (n = 117), 2 (1.7%) had MOGAD (K-FLC index of 7.9 and 16.2) and 99 (85%) MS/CISwc. Among patients with normal MRI (n = 96), 73 (76%) had a K-FLC index <4.9: 22 of these (30%) had MOGAD, and none showed conversion to MS. Among the remaining patients with a K-FLC index ≥4.9 (n = 23), 2 (8.5%) had MOGAD and 7 (30.5%) showed conversion to MS. The K-FLC index did not differentiate NMOSD from other diagnoses and only moderately differentiated NMO from MS/CISwc (AUC 0.80). DISCUSSION: The K-FLC index is an accessible biomarker to guide early diagnosis in patients with ION. The probability of MOGAD in patients with ION and a K-FLC index ≥4.9 is low even in case of normal brain/spinal cord MRI. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that for patients with ION, the K-FLC index can distinguish between MS/CISwc and MOGAD.
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