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Background and purpose: Cerebrospinal fluid (CSF) kappa free light chains (FLCs) may be a more sensitive marker of intrathecal immunoglobulin (Ig)G synthesis compared with oligoclonal bands (OCBs). Our aim was to retrospectively determine the additional value of the kappa and lambda index (CSF FLC/serum FLC)/(CSF albumin/serum albumin) in predicting a multiple sclerosis (MS) diagnosis in a group of OCB‐negative patients with suspected MS. Methods: The CSF and serum kappa and lambda FLCs were tested using the Freelite kit (serum) and Freelite Mx (CSF) assay (The Binding Site Group, Bimingham, UK) in 391 OCB‐negative patients with suspected/possible MS and in 54 OCB‐positive patients with MS. Results: The CSF kappa FLC levels were below the detection limit (0.27 mg/L) in 61% of patients. Using quantitative data, we found the best kappa index cut‐off value for the prediction of MS to be 5.8. A kappa index ≥5.8 was present in 25% of OCB‐negative MS (23/92) and in 98% of OCB‐positive patients with MS. Using a qualitative approach and a kappa index cut‐off of 5.9, based on literature data, we likewise found that 24% of OCB‐negative patients with MS had a kappa index ≥5.9, compared with 5.4% of OCB‐negative patients without MS (P < 0.001). No reliable data could be obtained for the lambda index; lambda FLCs were below the detection limit (0.68 mg/L) in 90% of CSF samples. Conclusions: The kappa index could contribute to the identification of OCB‐negative patients with a high probability of an MS diagnosis. Using more sensitive techniques might even improve the diagnostic performance of the kappa index and better define the role of the lambda index. [ABSTRACT FROM AUTHOR]

Background and Purpose: This study was undertaken to highlight neonatal Fc receptor inhibition (efgartigimod) as a valuable therapeutic option for patients with refractory seronegative myasthenia gravis (MG) and to emphasize the concept that seronegative MG is greatly constrained by the limitations of currently available diagnostic methods and therapeutic measures., Methods: We describe the first refractory, generalized MG (gMG) patient successfully treated with efgartigimod after testing negative on standard autoantibody detection tests., Results: Our patient presented with severe fluctuating bulbar and generalized weakness, resulting in multiple myasthenic crises requiring intubation. After a 28-year medical history of multiple failed lines of treatment, our patient was started on efgartigimod. Over five treatment cycles, a definite improvement in her clinical condition was observed (Myasthenia Gravis Foundation of America class: IIIb to IIb; MG-Activities of Daily Living score: 11 to 0; MG-Quality of Life 15 score: 30 to 0; Quantitative MG score: 28 to 6). Standard autoantibody detection tests failed to detect known pathogenic autoantibodies, but cell-based assay (CBA) identified autoantibodies against clustered adult acetylcholine receptor (AChR)., Conclusions: In light of recent approvals of efgartigimod by the European Medicines Agency and US Food and Drug Administration exclusively for AChR-positive gMG forms, our case highlights evidence suggesting that such an approach might be shortsighted and could limit therapeutic options for patients with refractory seronegative gMG. Additionally, introducing more sensitive analytical techniques, exemplified by CBA, may help bridge the gap between seronegative and seropositive patients. This represents an urgent unmet need for gMG patients, as the antibody profile dramatically influences the therapeutic approach., (© 2024 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)

Background and Purpose: Longitudinally extensive transverse myelitis (LETM) associated with aquaporin-4 autoantibodies (AQP4-IgG) can cause severe disability. Early diagnosis and prompt treatment are critical to prevent relapses. A novel score is described based on clinical and neuroimaging characteristics that predicts AQP4-IgG positivity in patients with LETM., Methods: Patients were enrolled both retrospectively and prospectively from multiple Italian centers. Clinical and neuroimaging characteristics of AQP4-IgG positive and negative patients were compared through univariate and multivariate analysis., Results: Sixty-six patients were included. Twenty-seven (41%) were AQP4-IgG positive and median age at onset was 45.5 years (range 19-81, interquartile range 24). Female sex (odds ratio [OR] 17.9, 95% confidence interval [CI] 2.6-381.9; p = 0.014), tonic spasms (OR 45.6, 95% CI 3.1-2197; p = 0.017) and lesion hypointensity on T1-weighted images (OR 52.9, 95% CI 6.8-1375; p = 0.002) were independently associated with AQP4-IgG positivity. The AQP4-IgG positivity in myelitis (AIM) score predicted AQP4-IgG positivity with 85% sensitivity and 95% specificity. Positive and negative likelihood ratios were 16.6 and 0.2 respectively. The inter-rater and intra-rater agreement in the score application were both excellent., Conclusions: The AIM score predicts AQP4-IgG positivity with good sensitivity and specificity in patients with a first episode of LETM. The score may assist clinicians in early diagnosis and treatment of AQP4-IgG positive LETM., (© 2023 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)