Anti-NMDA receptor (NMDAR) encephalitis was first reported to develop in female young adults with ovarian teratoma. However, another study with a larger cohort reported that more than one-third of all patients with anti-NMDAR encephalitis were aged under 18 years, suggesting that this encephalitis might be more common in children than originally expected.
A clinical diagnostic approach to autoimmune encephalitis was proposed in 2016, and included diagnostic criteria for probable and definite anti-NMDAR encephalitis. For a diagnosis of probable anti-NMDAR encephalitis, the criteria require rapid onset (
We retrospectively reviewed clinical information of patients with neurologic symptoms whose CSF was analyzed for NMDAR antibodies (NMDAR-Abs) in our laboratory from January 1, 2015, to March 31, 2019.
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, 3 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 neurologic autoimmunity.
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 or lower level of suspicion for encephalitis in the pediatric population. Physicians should therefore continue differential diagnosis, focusing especially on other forms of encephalitis.
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