Clinical Criteria to Guide Antineuronal Antibody Testing for People With Early and Persistent Psychosis Attending Mental Health Services

Background Early detection of autoimmune psychosis (AP) mediated by antineuronal antibodies (Abs) is critical for achieving optimal clinical outcomes. However, evidence remains limited regarding who should be tested and how Ab-positive cases should be managed. In this large-scale study, we evaluated proposed clinical criteria for targeted Ab testing in psychiatric services and described the clinical course of seropositive patients. 

Methods: Individuals with early psychosis (EP) or persistent psychosis (PP) were prospectively assessed with clinical criteria to determine high- or low-risk status for AP. Blood samples were collected for Ab testing using a fixed cell-based assay. Seropositive individuals were invited for detailed review, including clinical, functional, and cognitive assessments at baseline and a 12-month follow-up. Blood samples were collected from 754 individuals (EP: n = 352, PP: n = 402).

Results: Abs were present in 2.3% (17/754), including 3.4% (12/352) of patients with EP and 1.2% (5/402) of patients with PP. AP was confirmed in 2 cerebrospinal fluid (CSF)–positive high-risk individuals (total: 2/754, 0.3%; EP: 1/352, 0.3%; PP: 1/402, 0.2%). Both improved with immunotherapy. Although some low-risk patients were seropositive, none were diagnosed clinically with AP. 

Conclusions: AP prevalence was low in this cohort. Targeted testing informed by clinical high-risk criteria successfully identified 2 immunotherapy-responsive AP cases. This approach appears feasible but requires further validation. People with psychosis and high-risk AP features should be considered for Ab testing in sera and CSF where indicated. Further research is required to embed targeted Ab testing into mental health services.