Autoimmune encephalitis in first episode psychosis: Prospective non-interventional longitudinal study in tertiary...

Autoimmune encephalitis (AE) comprises a group of immune-mediated central nervous system disorders and can present with psychiatric symptoms. This study aimed to prospectively identify and characterize the AE group in first psychotic episode (FEP) at the tertiary psychiatric hospital using clinical and instrumental data in combination with modified algorithm for AE in FEP; and retrospectively evaluate current diagnostic algorithms for AE and autoimmune psychosis (AP) based on obtained empirical data.

We consecutively assessed all FEP patients admitted to psychiatric hospital according to inclusion-exclusion criteria. In all included patient's clinical picture was assessed, serum and cerebrospinal fluid (CSF) were taken at the acute stage of disorders. CSF oligoclonal bands, cytosis and protein level were tested in all CSF samples. Serum antineuronal antibodies (Abs) to intracellular antigens, NMDA, CASPR2, LGi1, GABAb, AMPA1,2, GAD Abs, thyroid serology, ANA, dsDNA Abs were measured. After the warning signs assessment, the second set of analyses were performed in patients with "red flags" and/or positive laboratory tests: CSF antineuronal antibodies (NMDA, CASPR2, LGi1, GABAb, AMPA1,2, GAD Abs), brain MRI, and oncological screening. AE diagnosis was made by Graus criteria. Immunosuppressive treatment was used in AE patients. We assessed the outcome after the treatment, and for all patients after 9-12 months follow-up.

784 consecutive patients underwent the screening procedure as patients referred to the tertiary psychiatric hospital with FEP. After the inclusion/exclusion procedure, 143 patients were included in the study. We confirmed AE diagnosis in 5 patients (3.5 % of included patients): anti-AMPH, anti-AMPA 2, anti-GABAb, anti-yo AE, and AE with CSF antineuronal antibodies. 1 out of 5 patients died in the acute stage, 3 have good outcomes and return to work.

We revealed 3.5 % AE in the FEP cohort in an East-European tertiary psychiatric hospital. No clinical "red flags" were detected in 1 patient. In 1 patient Ab was detected only in CSF. AE criteria + "red flags" assessment help to reveal 4 out 5 cases. 1 case was found at serum screening and confirmed by CSF analysis. Our results supported the necessity of valid "red flags" panel, serum and CSF antibody testing in the FEP cohort at admission for improving AE diagnostics in FEP.