Influence of Autoimmune Antibody Testing on the Use of Immunotherapy on an Inpatient Neurology Service.

Objective: To determine the frequency of autoimmune antibody testing in an inpatient neurology setting and its influence on immunotherapy use on an inpatient neurology service.

Methods: A retrospective descriptive cohort study of patients admitted to the neurology inpatient service at a large tertiary academic medical center who had autoimmune and/or paraneoplastic antibody testing performed between 10/1/2017 and 10/1/2018. Characteristics of patients' initial clinical presentation, antibody testing results, test timing in relation to initiating immunotherapy, and final diagnosis using consensus criteria were extracted and analyzed. Case reports of patients with positive antibody panels are presented.

Results: Of 1,604 patients, 50 patients (3.1%) had an antibody panel sent. Tests resulted after an average of 17 days (range 7-27). The most common clinical presenting symptom in those with a panel sent was encephalopathy. There were 5 (10%) positive serum panels and no positive CSF panels. Only one of these 5 patients had autoimmune encephalitis and was treated with immunotherapy. Of those with negative serum and CSF panels, 15 were treated acutely with empiric immunotherapy and the remainder with supportive care. Of those treated with immunotherapy, 14/15 (93%) were treated before the panel tests resulted. Four patients who had negative panels but were empirically treated met consensus criteria for an autoimmune-mediated neurologic process.

Conclusion: Our study suggests that the results of antibody testing did not influence inpatient neurologists' decision to treat with immunotherapy as most treatments began prior to final results being available.