Abstract
Background Autoimmune encephalitis and paraneoplastic syndromes are increasingly considered as diagnoses for patients with diverse neurologic symptoms. Antibody testing is costly and labour intensive. The yield and impact on management of testing has not been defined.
Objectives To review clinical indications, management implications and yield of testing for cell-surface and intracellular neuronal antibodies.
Methods We retrospectively analysed all requested anti-neuronal and cell surface antibody tests from 2019 to 2022. Our data collection focused on Alfred Health – a tertiary hospital in Victoria. Data was collected on the clinical indication for testing, supportive investigations, diagnosis and management.
Results 731 tests from 200 patients were reviewed. The most indications for antibody testing were cognitive and psychiatric syndromes. 54 patients had cognitive impairment and 33 had psychiatric symptoms, 29 (53.7%) and 6 (18.2%) of which had associated seizures or focal neurology respectively. Other common indications included neuropathy (32), movement disorders (19), cerebellar syndromes (15) and seizures (18). Indications for the remaining 29 patients were heterogenous or unknown. Ten (5%) patients were diagnosed with autoimmune encephalitis and three (1%) with paraneoplastic syndromes. Two false positive for cell-surface antibodies and ten false positives for intracellular neuronal antibodies occurred. 37 (18.5%) patients received immunotherapy. Two patients’ management was altered by positive antibody results (LGI, anti-Yo).
Conclusion The indications for autoimmune encephalitis and paraneoplastic antibody testing were heterogenous. The yield of true positive results was low and infrequently changed management. Clinical phenotyping of patients with supportive investigations is important to prevent inappropriate widespread auto-antibody testing.
