The POWER-tool: Recommendations for involving patient representatives in choosing relevant outcome measures during rare disease clinical trial design.

In clinical trials, it is relevant to ask patients and/or their caregivers which aspects concerning their disease they consider important to measure when a new intervention is being investigated. Those aspects, useful as outcome measures in a trial, are of pivotal importance for the result of the trial and the subsequent decision-making. In rare diseases the choice of outcome measures may be even more important, due to the small numbers and heterogeneity of the patients that are included. We have developed a tool to involve patients in the determination of outcome measures and the choice of measurement instruments. This tool was developed together with a patient think tank, consisting of a group of rare disease patient representatives, and by interviewing end users. We have road-tested our tool in an ongoing trial, and evaluated it during a focus group meeting. The tool consists of three steps: 1) Preparation, 2) Consultation of patients, 3) Follow-up during which the consultation results are implemented in the trial design. The tool provides guidelines for researchers to include the patient's opinion in the choice of outcome measures in the trial design stage. We describe the development of the POWER-tool (Patient participation in Outcome measure WEighing for Rare diseases), and first experiences of the tool in an ongoing trial.