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

Autoimmune and paraneoplastic antibody testing has transformed our knowledge of previously indistinct neurologic presentations. However, little is known about its accuracy or impact on inpatient treatment decision-making.

A retrospective chart review of all patients admitted to the neurology inpatient service at a large tertiary academic medical center where autoimmune and/or paraneoplastic antibody testing was 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.   

Of 1604 patients admitted during the study period, fifty (3.1%) had an antibody panel sent from the CSF and/or serum. There were 43 CSF and 41 serum panels sent. Tests resulted after an average of 17 days (range 7-27). No CSF panels returned a positive result. The most common clinical presentation symptom in those with a panel was encephalopathy.

There were five positive serum panels. Only one of five patients had a relevant autoimmune syndrome (as determined by consensus guidelines) and was treated with immunotherapy. The other four patients with positive panels did not meet consensus criteria and were not treated with immunotherapy (“false positives”).

Of those with negative serum and CSF panels, fifteen were treated empirically with 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.

Our study suggests the results of autoimmune and paraneoplastic antibody testing did not influence neurohospitalists’ decision to treat with immunotherapy as most treatments began prior to final results being available.