Evaluation of the Diagnostic Criteria for Anti-NMDA Receptor Encephalitis in Japanese Children.

OBJECTIVE: To evaluate the validity of the 2016 clinical diagnostic criteria proposed for probable anti-NMDA receptor (NMDAR) encephalitis in children, we tested the criteria in a Japanese pediatric cohort. METHODS: We retrospectively reviewed clinical information of patients with neurological symptoms whose CSF were analyzed for NMDAR antibodies (Abs) in our laboratory from January 1, 2015, to March 31, 2019. RESULTS: Overall, 137 cases were included. Of the 41 cases diagnosed as probable anti-NMDAR encephalitis (“criteria-positive”) according to the 2016 criteria, 13 were positive and 28 were negative for anti-NMDAR Abs. Of the 96 criteria-negative cases, three were positive and 93 were negative for anti-NMDAR Abs. The sensitivity of the criteria was 81.2%, specificity was 76.9%, positive predictive value (PPV) was 31.7%, and negative predictive value was 96.9%. Compared with the true-positive group, the false-positive group contained more male than female patients (male:female, 4:9 in the true-positive vs. 19:9 in the false-positive group, p = 0.0425). The majority of the cases with false-positive diagnoses were associated with neurological autoimmunity. CONCLUSION: The clinical diagnostic criteria are reliable for deciding to start immunomodulatory therapy in the criteria-positive cases. Low PPV may be caused by a lower prevalence of NMDAR encephalitis and/or lower level of suspicion for encephalitis in the pediatric population. Physicians should therefore continue differential diagnosis, focusing especially on other forms of encephalitis. Classification of Evidence: This study provides Class IV evidence that the proposed diagnostic criteria for anti-NMDAR encephalitis in children has a sensitivity of 81.2% and a specificity of 76.9%.