Autoimmune encephalitis timing and incidence: the Manitoba experience (577)

Objective: To determine whether empiric treatment(s) are initiated or delayed prior to availability of antibody test results in patients with suspected autoimmune encephalitis within the Canadian province of Manitoba. Background: Autoimmune encephalitis is a serious yet treatable antibody-mediated inflammatory condition of the central nervous system. Early treatments have been shown to improve functional recovery. Despite expert recommendation, it remains unclear if clinicians consistently initiate empiric treatments prior to availability of antibody results in patients with suspected autoimmune encephalitis. Design/Methods: We conducted retrospective chart reviews of patients referred for autoimmune encephalitis testing from the provincial immunology laboratory. Primary outcomes were the proportions of patients receiving treatments prior to the availability of antibody results. Clinical presentations, investigations, complication rates, mortality rates, and durations of hospital and intensive care admission were secondary outcome measures. Results: We identified 151 patients who had autoimmune encephalitis antibody testing done in 2012–2018. We included 43 patients who met suspected autoimmune encephalitis criteria. The annual incidence of autoimmune encephalitis in Manitoba was 0.30 per 100,000. 28/43 (65%) patients were treated prior to availability of antibody results (“Early group”). 15/43 (35%) patients did not receive treatment prior to availability of antibody results (“Late group”). Significantly more Early group patients had repeat immunotherapy (p=0.001), abnormal MRI findings (p=0.027), and investigations for malignancy (p=0.015). Durations of hospital and intensive care admission, complication rates, and mortality rates were not different between the two groups. Conclusions: This is the first-ever autoimmune encephalitis incidence, timing, and management study of a comprehensive Canadian geopolitical and medical catchment area. Over the course of seven years, approximately one-third of patients with suspected autoimmune encephalitis were not treated prior to availability of antibody results. Patients treated earlier did not experience greater treatment-related or hospitalization-related complications. We hope our findings inspire increased recognition for earlier treatment in patients with autoimmune encephalitis. Disclosure: Dr. Nguyen has nothing to disclose. Dr. Xu has nothing to disclose. Dr. Ng has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Eisai.