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Induction and Clinical Scoring of Chronic-Relapsing Experimental Autoimmune Encephalomyelitis
Published on: July 4, 2007
Kappa index in the diagnostic work-up of autoimmune encephalitis
Giulia De Napoli1, Matteo Gastaldi2, Patrizia Natali3
1Department of Biomedical, Metabolic and Neurosciences, University of Modena and Reggio Emilia, Modena, Italy; Department of Neurosciences, Ospedale Civile di Baggiovara, Azienda Ospedaliero-Universitaria of Modena, Modena, Italy.
Insights
The Kappa index, a marker for immunoglobulin intrathecal synthesis (IS), shows promise in diagnosing autoimmune encephalitis (AE). This neuroinflammation marker may be more sensitive than traditional tests like oligoclonal bands (OCB).
Area of Science:
- Neurology
- Immunology
- Clinical Diagnostics
Background:
- Autoimmune encephalitis (AE) diagnosis relies on detecting inflammatory changes in cerebrospinal fluid (CSF), including immunoglobulin intrathecal synthesis (IS).
- Prompt AE diagnosis and treatment are crucial for patient outcomes.
Purpose of the Study:
- To evaluate the Kappa index as a marker for IS in patients with suspected AE.
- To assess the sensitivity of the Kappa index compared to traditional markers like oligoclonal bands (OCB).
Main Methods:
- Retrospective review of AE patient charts (2009-2023) using Graus criteria.
- Measurement of CSF and serum kappa free light chains using Freelite assay and Optilite analyzer.
Main Results:
- In definite AE patients, the Kappa index was >6 in 29.4% and >3 in 50%.
- Elevated Kappa index (>3) was observed in 36.4% of definite AE patients negative for OCB.
- The Kappa index identified neuroinflammation in three definite AE patients with otherwise normal CSF parameters.
Conclusions:
- The Kappa index may serve as a sensitive marker for IS in AE diagnosis.
- It can be a valuable supportive marker for neuroinflammation in suspected AE cases.
Background:
The presence of inflammatory changes in the cerebrospinal fluid (CSF), including immunoglobulin intrathecal synthesis (IS), can support the diagnosis of autoimmune encephalitis (AE) and allow prompt treatment. The main aim of our study was to calculate the Kappa index as a marker of IS, in patients with AE.
Methods:
Charts of patients undergoing a diagnostic work-up for suspected AE between 2009 and 2023 were reviewed and the Graus criteria applied. CSF and serum kappa free light chains were determined using the Freelite assay (The Binding Site Group) and the turbidimetric Optilite analyzer.
Results:
We identified 34 patients with "definite" AE (9 anti-NMDAR AE and 25 limbic AE) and nine patients with "possible" AE. Five patients (15%) with definite AE had pleocytosis and twelve (34%) showed CSF-restricted oligoclonal bands (OCB) at isoelectric focusing. The Kappa index was >6 in 29.4% and > 3 in 50% of the definite AE patients. It was elevated (>3) in 36.4% of patients with definite AE who resulted negative to OCB testing and was the only altered parameter suggestive of an ongoing inflammatory process in the CNS in three definite AE patients with otherwise normal CSF findings (i.e. normal cell count and protein levels, no OCBs). In the possible AE group, one patient had a Kappa index >3 in the absence of OCB.
Conclusions:
The Kappa index could be useful, as a more sensitive marker of IS and as a supportive marker of neuroinflammation, in the diagnostic work-up of suspected AE.
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