P.030 Antibody testing for autoimmune encephalitis: a multisite study examining clinical practices in a large Canadian city

Abstract

Background: Antibody panels are one diagnostic tool within the comprehensive evaluation of suspected autoimmune encephalitis (AIE). Over-reliance on antibody panels contributes to misdiagnosis and inflated healthcare costs. Methods: Inpatients or outpatients who had AIE antibody testing ordered from one of four adult hospitals in Calgary between January 2018 – January 2020 were included. Medical records of 150 individuals were reviewed, including those with positive antibodies or testing sent to Mayo Clinic, plus a random sample. Results: AIE antibody panels were sent for 469 individuals during the 2-year period; 42 were positive (9.0%) of which 10 were pathogenic. Of 150 individuals included in chart review, 27 (18.0%) met criteria for possible AIE at presentation and 16 (10.8%) met criteria for definite AIE at final diagnosis. Overall, antibody testing was ordered in both serum and CSF in 36.3% (versus 69.2% meeting possible AIE criteria); MRI brain was performed in 92.7% (possible AIE 92.6%), EEG in 78.7% (possible AIE 100.0%), and lumbar puncture in 66.7% (possible AIE 96.3%). A sizable proportion did not receive malignancy screening (overall 48.7%; possible AIE 29.6%). Conclusions: Antibody panels are overemphasized in the assessment for AIE and often performed unnecessarily, while other recommended clinical tests are not consistently completed.