Development of core outcome sets for effectiveness trials of interventions to prevent and/or treat delirium (Del-COrS): study protocol.

INTRODUCTION: Delirium is a common, serious and potentially preventable condition with devastating impact on the quality of life prompting a proliferation of interventional trials. Core outcome sets aim to standardise outcome reporting by identifying outcomes perceived fundamental for measurement in trials of a specific interest area. Our aim is to develop international consensus on two core outcome sets for trials of interventions to prevent and/or treat delirium, irrespective of study population. We aim to identify additional core outcomes specific to the critically ill, acutely hospitalised patients, palliative care and older adults.

METHODS AND ANALYSIS: We will conduct a systematic review of published and ongoing delirium trials (1980 onwards) and one-on-one interviews of patients who have experienced delirium and family members. These data will inform Delphi round 1 of a two-stage consensus process. In round 2, we will provide participants their own response, summarised group responses and those of patient/family participants for rescoring. We will randomise participants to receive feedback as proportion scoring the outcome as critical or as group mean responses. We will hold a consensus meeting using nominal group technique to finalise outcomes for inclusion. We will repeat the Delphi process and consensus meeting to select measures for each core outcome. We will recruit 240 Delphi participants giving us 80% power to detect a 1.0-1.5 point (9-point scale) difference by feedback method between rounds. We will analyse differences for subsequent scores, magnitude of opinion change, items retained and level of agreement.

ETHICS AND DISSEMINATION: We are obtaining research ethics approvals according to local governance. Participation will be voluntary and data deidentified. Support from three international delirium organisations will be instrumental in dissemination and core outcome set uptake. We will disseminate through peer-reviewed open access publications and present at conferences selected to reach a wide range of knowledge users.