Cerebrospinal Fluid
GAD65
‐Antibody Levels Accurately Identify Relevant Neurological Diseases
Max Charles Herman, Maya Marzello, Zoaib Habib Tharwani, Snigdha Kotaru, Yoav D. Piura, Eric Newman, Gregory S. Day, Andrew McKeon, A. Sebastian Lopez‐Chiriboga, Sarosh R. Irani ABSTRACT
Retrospective cohort study to investigate which factors most reliably distinguish incidental GAD65‐antibodies (iGAD65) from true GAD65‐antibody neurological disease (tGAD65). 167 adults with positive serum and CSF GAD65‐antibodies (> 0.02 nmol/L by radioimmunoassay) were classified as tGAD65 or iGAD65, with diagnostic performance of paraclinical parameters compared in discovery and validation cohorts. CSF GAD65‐antibody titers ≥ 1 nmol/L performed best in discovery (AUC 0.956) and validation (AUC 0.949; p = 0.814), with 89.7% sensitivity and 94% specificity for identifying tGAD65. Serum titers > 20 nmol/L and indices of intrathecal synthesis showed lower discriminative ability. Our finding aims to reduce misdiagnosis and identify potential immunotherapy‐responsive diseases.