Advertising patient and public involvement in trials as a way of improving participant recruitment: development of an intervention and its evaluation

Methods The principles underlying the intervention were informed by a systematic review and a workshop that included mental health service users, trialists and ethicists. We recruited mental health trials with high quality PPI, and worked with PPI members in each trial to develop the intervention using a leaflet to advertise the nature and function of the PPI. Professional graphic design optimised readability and impact. Potential participants in each host trial will be randomised to receive the leaflet or not, alongside the standard study information. The effectiveness of the leaflet will be evaluated within and across trials.