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@ARTICLE{Groeger:281861,
      author       = {Groeger, Luise M and Brinke, Kristina Auf dem and Simou,
                      Amina and Luedecke, Daniel and Maier, Hannah B and Neyazi,
                      Alexandra and Gallinat, Jürgen and Bleich, Stefan and
                      Skripuletz, Thomas and Konen, Franz F and Wiltfang, Jens and
                      Malchow, Berend and Fitzner, Dirk and Hansen, Niels},
      collaboration = {CAP},
      title        = {{S}erum and cerebrospinal kappa free light chains in
                      psychiatric syndromes with neuronal and paraneoplastic
                      autoantibodies.},
      journal      = {Behavioural brain research},
      volume       = {496},
      issn         = {0166-4328},
      address      = {Amsterdam},
      publisher    = {Elsevier},
      reportid     = {DZNE-2025-01234},
      pages        = {115858},
      year         = {2026},
      abstract     = {Kappa free light chains (KFLC) are a surrogate parameter
                      for intrathecal immunoglobulin G (IgG), immunoglobulin M
                      (IgM) and immunoglobulin A (IgA) synthesis confirming
                      neuroinflammation in the central nervous system (CNS). It is
                      unclear whether KFLC can differentiate primary psychiatric
                      disorders from neural autoantibody-associated psychiatric
                      syndromes.We enrolled 76 patients with psychiatric diagnoses
                      ICD-10 (International Classification of Diseases, 10th
                      revision) (F00-09, F10-19, F20-29, F30-39, F40-49) and
                      cerebrospinal fluid (CSF) as well as blood samples from our
                      biobank. Commercial assays were used to determine neural
                      autoantibodies. KFLC in serum and CSF samples were assessed
                      by nephelometry (Siemens Atellica NEPH 630 analyzer). We
                      calculated the relative intrathecal fraction (IF) of KFLC
                      and the KFLC index using KFLC quotient and albumin quotient.
                      Criteria for autoimmune encephalitis and autoimmune-mediated
                      psychiatric syndromes were evaluated in patients to
                      determine an autoimmune basis for the psychiatric
                      symptoms.Neither the number of patients with elevated KFLC,
                      a KFLC index nor the KFLC IF percentage served as an
                      instrument for differentiating between autoantibody-positive
                      (n = 18) and autoantibody-negative (n = 58) psychiatric
                      patients. Patients with elevated KFLC levels in CSF had a
                      higher proportion of lymphocytes than patients with
                      non-elevated KFLC as a non-significant trend. We observed a
                      non-significant trend towards higher CSF/serum IgM, but no
                      trend for CSF/serum IgA or CSF/serum IgG ratio in patients
                      with elevated KFLC levels than in those with non-elevated
                      KFLC. No probable autoantibody-positive or seronegative
                      autoimmune encephalitis was detected in patients. However,
                      we observed an autoantibody-associated psychiatric syndrome
                      in 6 out of 10 patients with elevated KFLC-IF, and the
                      detection of elevated KFLC improved the diagnosis of
                      probable autoimmune disease in 4 out of 10 patients (40
                      $\%).Elevated$ KFLC levels may indicate psychiatric patients
                      presenting any intrathecal immunoglobulin synthesis and thus
                      help to evaluate an autoimmune basis in psychiatric
                      syndromes. Furthermore, it should be added as a novel
                      criterion for intrathecal immunoglobulin synthesis in
                      autoimmune-related psychiatric syndromes. Further
                      large-scale research is needed to elucidate the role of KFLC
                      in autoimmune-mediated psychiatric disorders and to verify
                      the observed trends in CSF parameters in patients with
                      elevated KFLC.},
      keywords     = {Humans / Autoantibodies: blood / Autoantibodies:
                      cerebrospinal fluid / Female / Male / Middle Aged / Adult /
                      Mental Disorders: blood / Mental Disorders: cerebrospinal
                      fluid / Mental Disorders: immunology / Mental Disorders:
                      diagnosis / Aged / Immunoglobulin kappa-Chains: blood /
                      Immunoglobulin kappa-Chains: cerebrospinal fluid /
                      Encephalitis: immunology / Encephalitis: blood /
                      Encephalitis: cerebrospinal fluid / Encephalitis: diagnosis
                      / Hashimoto Disease: blood / Hashimoto Disease:
                      cerebrospinal fluid / Hashimoto Disease: immunology /
                      Hashimoto Disease: diagnosis / Biomarkers: blood /
                      Biomarkers: cerebrospinal fluid / Young Adult /
                      Autoantibodies (Other) / Kappa free light chains (Other) /
                      Psychiatry (Other) / Autoantibodies (NLM Chemicals) /
                      Immunoglobulin kappa-Chains (NLM Chemicals) / Biomarkers
                      (NLM Chemicals)},
      cin          = {AG Wiltfang},
      ddc          = {610},
      cid          = {I:(DE-2719)1410006},
      pnm          = {353 - Clinical and Health Care Research (POF4-353)},
      pid          = {G:(DE-HGF)POF4-353},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:41038324},
      doi          = {10.1016/j.bbr.2025.115858},
      url          = {https://pub.dzne.de/record/281861},
}