Clinical Outcome Assessments in Encephalitis: A Systematic Review

Background and Objectives
Most patients with encephalitis experience persisting neurocognitive and neuropsychiatric sequelae in the years following this acute illness. Reported outcomes are often based on generic clinical outcome assessments that rarely capture the patient perspective. This may result in an underestimation of disease-specific sequelae. Disease-specific clinical outcome assessments can improve clinical relevance of reported outcomes and increase the power of research and trials. There are no patient-reported outcome measures (PROMs) developed or validated specifically for patients with encephalitis. The primary objective of this systematic literature review was to identify PROMs that have been developed for or validated in patients with encephalitis.

Methods
We performed a systematic review of the literature published from inception until May 2023 in 3 large international databases (MEDLINE, EMBASE and Cochrane libraries). Eligible studies should have developed or validated a PROM in patients with encephalitis or encephalopathy. Methodologic quality was evaluated using the Consensus-based Standards for the selection of health status Measurement Instruments study design checklist for PROMs.

Results
We identified no disease-specific PROMs developed or validated for patients with encephalitis. We identified one study on the development and validation of a disease-specific PROM for hepatic encephalopathy, although this disease course is substantially different to that of patients with encephalitis. The methodologic quality of the included study was generally rated as "doubtful." We identified 30 PROMs that have been applied in 46 studies on encephalitis or encephalopathy, although not validated in these populations. The most commonly applied PROMs for measuring Health-Related Quality of Life were the Medical Outcomes Study Short Form-36 and the Sickness Impact Profile. Emotional well-being was often assessed with the Beck Depression Inventory (BDI-II). Sporadically, PROMs were applied to address other aspects of outcome including daily functioning and sleep quality.

Discussion
This systematic review confirms a critical gap in clinical outcome assessments in patients with encephalitis, failing to identify a validated measuring tool for detecting neurocognitive, functional, and health status. It is therefore essential to develop and/or validate disease-specific PROMs for the population with encephalitis to capture relevant information for patient management and clinical trials about the effects of disease that are at risk of being overlooked.