Using a behavioural approach to explore the factors that affect questionnaire return within a clinical trial: a qualitative study based on the theoretical domains framework

Objectives To identify barriers and enablers to participant retention in trials requiring questionnaire return using the theoretical domains framework (TDF). Study design and setting We identified and subsequently invited participants who did not return at least one questionnaire during their participation in a clinical trial for one-to-one semi-structured telephone interviews. We used a behavioural framework (TDF) to explore whether any of the behavioural domains (eg, beliefs about consequences, emotion) affected questionnaire return. Thereafter, we generated a series of belief statements which summarised the content of participants' main responses and coded these under separate themes. Participants We distributed invites to 279 eligible individuals and subsequently interviewed 9 participants who took part in the C-Gall trial. The C-Gall trial required participants to complete five postal questionnaires during their participation. Results Nine participants were interviewed. We developed 7 overarching themes which were relevant for returning postal questionnaires and identified both barriers and enablers from 11 core domains: knowledge; beliefs about consequences; environmental context and resources; reinforcement; emotion; beliefs about capabilities; behavioural regulation; social professional role and identity; skills; intentions and goals. Relevant content coded under these salient domains were categorised into seven key themes: unclear expectations of trial participation, personal attributes for questionnaire return, commitment to returning questionnaires given other priorities, sources of support in returning the questionnaires, individual preferences for presentation mode and timing of the questionnaires, internal and external strategies to encourage questionnaire return and the significance of questionnaire non-return. Conclusion We demonstrate how a behavioural approach may be useful for clinical trials associated with significant participation burden (e.g. trials that require multiple questionnaire responses), acting as the essential groundwork for the development of appropriate evidence-based solutions to combat retention issues.