Validation of the encephalitis criteria in adults with a suspected central nervous system infection: An updated score.

Objectives: We aimed to validate and refine the encephalitis criteria proposed by the International Encephalitis Consortium in a cohort of adults initially suspected of a central nervous system (CNS) infection.

Methods: We included patients from two prospective cohort studies consisting of adults suspected of a CNS infection whom underwent a diagnostic lumbar puncture. We evaluated the test characteristics of the criteria for both possible and probable encephalitis. The reference standard was a final clinical diagnosis of encephalitis. Recalibration of the criteria was done by adjusting the weight of each criterion based on their respective odds.

Results: In total 1446 episodes were evaluated, of whom 162 (11%) had a clinical diagnosis of encephalitis. Possible encephalitis had a sensitivity of 41% (95% CI 33-49) and a specificity of 88% (95% CI 86-90). Probable encephalitis had a sensitivity and specificity of respectively 27% (95% CI 20-34) and 95% (95% CI 94-96). Through odds-based weighting, we recalibrated the weight of each individual criterion, resulting in a model consisting of an altered mental status (weight of 2), seizures (weight of 3), elevated CSF leukocytes (weight of 5) and abnormalities on neuroimaging (weight of 9). We proposed a cut-off at 5 for possible encephalitis, (sensitivity 93% [95% CI 88-96]; specificity 51% [95% 49-54]), and at 8 for probable encephalitis (sensitivity 51% [95% CI 44-59]; specificity 91% [95% CI 89-92]).

Conclusions: We validated and refined the existing diagnostic criteria for encephalitis, leading to a substantially enhanced sensitivity. These updated criteria hold promise to facilitate the accurate identification of encephalitis.