Unpacking the 'black box of horrendousness': a qualitative exploration of the barriers and facilitators to conducting trials involving adults lacking capacity to consent

Background Trials involving adults who lack capacity to consent encounter a range of ethical and methodological challenges, resulting in these populations frequently being excluded from research. Currently, there is little evidence regarding the nature and extent of these challenges, nor strategies to improve the design and conduct of such trials. This qualitative study explored researchers’ and healthcare professionals’ experiences of the barriers and facilitators to conducting trials involving adults lacking capacity to consent. Methods Semi-structured interviews were conducted remotely with 26 researchers and healthcare professionals with experience in a range of roles, trial populations and settings across the UK. Data were analysed using thematic analysis. Results A number of inter-related barriers and facilitators were identified and mapped against key trial processes including during trial design decisions, navigating ethical approval, assessing capacity, identifying and involving alternative decision-makers and when revisiting consent. Three themes were identified: (1) the perceived and actual complexity of trials involving adults lacking capacity, (2) importance of having access to appropriate support and resources and (3) need for building greater knowledge and expertise to support future trials. Barriers to trials included the complexity of the legal frameworks, the role of gatekeepers, a lack of access to expertise and training, and the resource-intensive nature of these trials. The ability to conduct trials was facilitated by having prior experience with these populations, effective communication between research teams, public involvement contributions, and the availability of additional data to inform the trial. Participants also identified a range of context-specific recruitment issues and highlighted the importance of ‘designing in’ flexibility and the use of adaptive strategies which were especially important for trials during the COVID-19 pandemic. Participants identified a need for better training and support. Conclusions Researchers encountered a number of barriers, including both generic and context or population-specific challenges, which may be reinforced by wider factors such as resource limitations and knowledge deficits. Greater access to expertise and training, and the development of supportive interventions and tailored guidance, is urgently needed in order to build research capacity in this area and facilitate the successful delivery of trials involving this under-served population