Why trials lose participants: a multi-trial investigation of participants’ perspectives using the theoretical domains framework

Rumana Newlands, Eilidh Duncan, Justin Presseau, Shaun Treweek, Louisa Lawrie, Peter Bower, Jim Elliott, Jill J Francis, Graeme MacLennan, Margaret Ogden, Mary Wells, Miles D Witham, Bridget Young, Kate Gillies* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)
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To use the Theoretical Domains Framework (TDF) to identify barriers and enablers to participant retention in trials requiring questionnaire return and/or attendance at follow-up clinics.

Study design and setting

We invited participants (n=607) from five pragmatic effectiveness trials, who missed at least one follow-up time point (by not returning a questionnaire and/or not attending a clinic visit), to take part in semi-structured telephone interviews. The TDF informed both data collection and analysis. To establish what barriers and enablers most likely influence the target behaviour the domain relevance threshold was set at >75% of participants mentioning the domain.


Sixteen participants (out of 25 showing interest) were interviewed. Overall, seven theoretical domains were identified as both barriers and enablers to the target behaviours of attending clinic appointments and returning postal questionnaires. Barriers frequently reported in relation to both target behaviours stemmed from participants’ knowledge, beliefs about their capabilities and the consequences of performing (or not performing) the behaviour.. Two domains were identified as salient for questionnaire return only: goals; and memory, attention and decision-making. Emotion was identified as relevant for clinic attendance only.


This is the first study informed by behavioural science to explore trial participants’ accounts of trial retention. Findings will serve as a guiding framework when designing trials to limit barriers and enhance enablers of retention within clinical trials.

Original languageEnglish
Pages (from-to)P1-13
Number of pages13
JournalJournal of Clinical Epidemiology
Early online date12 Mar 2021
Publication statusPublished - 1 Sept 2021

Bibliographical note

We would like to thank all of the participants who volunteered and gave up their time to contribute to this study. We would also like to thank all of the teams linked to the host trials we worked with to help identify potential participants.

This research is funded by the Chief Scientist Office of the Scottish Government’s Health and Social Care Depart- ment [HIPS/16/46]. KG held a Medical Research Council UK Methodology Fellowship during the delivery of this project [MR/L01193X/1]. MDW acknowledges support from the NIHR Newcastle Biomedical Research Centre. Infrastructure support for this research was provided by the NIHR Imperial Biomedical Research Centre (BRC) to support MW.
The Health Services Research Unit, Institute of Applied Health Sciences (University of Aberdeen), is core-funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. The funders had no involvement in study design, collection, analysis and interpretation of data, reporting or the decision to publish.


  • randomised trials
  • retention
  • follow up
  • behaviour
  • theory


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