When confusion abounds: guideline adherence in the investigation and management of encephalitis in Sydney, Australia

Background Encephalitis is a condition of brain dysfunction and parenchymal inflammation with many aetiologies. Guidelines for Australia and Aotearoa New Zealand on diagnosis and management were published in 2015. There have been no recently published local studies of encephalitis. Aims This study assessed guideline adherence for recommended investigations and antimicrobial management of suspected community‐acquired encephalitis cases. Secondary aims were to compare clinical diagnoses to the International Encephalitis Consortium (IEC) consensus case definition and to provide descriptive epidemiology of encephalitis in Sydney, Australia. Methods A retrospective review of medical records was conducted for all adults with a cerebrospinal fluid (CSF) sample collected between 1 July 2018 and 30 June 2019 to investigate suspected community‐onset meningoencephalitis or encephalitis at four Sydney metropolitan hospitals. Results Two hundred and nine suspected cases were reviewed including 35 ultimately diagnosed as encephalitis. Adherence to guideline recommendations was variable but overall better in cases subsequently diagnosed as encephalitis, significantly so for some investigations. Viral polymerase chain reaction testing of non‐CSF samples, serology for human immunodeficiency virus and syphilis, repeat herpes simplex virus (HSV) PCR when indicated and anti‐N‐methyl‐D‐aspartate receptor antibody testing were areas for improvement. Empiric aciclovir was not given in 30% of suspected cases but was at the appropriate dose and frequency when prescribed. Ten of 35 cases with clinical encephalitis diagnoses did not meet the IEC case definition criteria. The most common infectious aetiology was HSV, while the most common mimics were drug‐associated presentations. Conclusions Guideline application was variable, with areas identified for improvement. Prospective studies are needed to investigate guideline‐adherence barriers.