To evaluate whether antibody screening using an in-house tissue-based assay (TBA) facilitates the early identification of autoimmune encephalitis (AE) and leads to prompt induction of immunotherapy in patients with encephalitis.

This prospective study was approved by our institutional review board. The study enrolled all adult patients with encephalitis admitted to our institution from July 1, 2017 to August 31, 2020. An in-house TBA, which was an immunohistochemical assay involving frozen rat brain sections, was used for antibody screening of cerebrospinal fluid. In samples with positive or questionable results, the specific antigens of the antibodies were confirmed by a cell-based assay or line blot.

 The study included 109 patients with encephalitis. The median patient age was 47 (16–80) years, and 66 were female. The samples of 28 patients were positive in TBA (13 with typical neuropil [9 NMDAR, 3 LGI1, and 1 GABA_B], 1 atypical [GAD 65], 4 onconeural [1 ANNA1, 2 Yo, 1 Sox1], 5 astrocytic [3 AQP4 and 2 GFAP], 1 white matter [MOG], and 4 positive in TBA alone [CBA negative]). The median interval for the screening result was 2 (2–5) days. All patients, except those with onconeural antibodies, responded well to intensive immunotherapy and showed a favorable outcome (median mRS 2). Of the 28 patients, 4 received intravenous cyclophosphamide, with positive TBA results before antigen confirmation.