Introduction The assessment of patient reported outcomes following neurological injury remains a challenging area of neurocritical care research. Mortality amongst the neurocritical patient population remains high with a significant proportion of survivors left suffering functional, cognitive and emotional deficits, often with a reduced health-related quality of life and leaving them dependent on caregivers. Numerous instruments have been developed to assess the level of impairment patients experience following a global neurological injury. Previous systematic reviews have reported significant heterogeneity in outcome assessment in neurocritical car trials, including the outcome measure used, method of ascertainment and the timing of outcome assessment. It has been suggested that this heterogeneity in outcome assessment has complicated the design of neurocritical care clinical trials, the pooling and meta-analysis of trial data and has led to conflicting and controversial trial results. It is unclear what impact the methods of performing outcome assessment has on loss follow up rates and the validity of outcome data in neurocritical care trials. We aim to systematically review the methods of performing outcome assessment in neurocritical care trials to identify current trends in outcome assessment in this patient population and to examine loss to follow up rates and factors impacting cohort attrition. It is hoped that an understanding of the relationship between methods of outcome assessment and loss to follow up will inform future design of neurocritical care trials. Methods and analysis This systematic review will include randomized clinical trials and large prospective observational cohort studies where the included population is adults with a diagnosis of traumatic brain injury or a subarachnoid haemorrhage and reporting at least one patient reported outcome measure. Inclusion will not be limited based on intervention nor comparator. We will limit the searches to human studies, with reports published in the English language and published within the last 10 years. We will search the Medline, EMBASE, and The Cochrane Central registry of clinical trial (CENTRAL) for eligible trials. We will manually search the reference list of relevant primary review articles, clinical registries, and abstracts from recent relevant conferences Conclusion This systematic review and will provide clinicians with an understanding of the relationship between methods of outcome assessment and loss to follow up will inform future design of neurocritical care trials.

The authors have declared no competing interest.

There is no external funding for this review. The Malcolm Fisher Department of Intensive Care Medicine at Royal North Shore Hospital is providing in-kind support for this review.

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