Complexities of retention in primary care randomised trials: A thematic analysis of in-depth interviews

Introduction Loss to follow-up in randomised trials can cause bias, compromise study power, and affect the generalisability and reliability of results [1]. Many strategies are used to try to retain participants, however little is known about trialists’ experiences of implementing such strategies, or their perspectives of effectiveness. The complexity of these experiences and perceptions may influence the type of strategies used in different disease areas and with different population groups. We explored factors that trialists think contribute to loss to follow-up in primary care randomised trials, and whether some strategies to improve retention are perceived to be more successful than others.