What is the best way to avoid recruitment and retention problems in trials?

What is the best way to avoid recruitment and retention problems in trials?

PhD Project - Dr Adel El Feky

Many trials struggle to recruit and retain participants and recruitment and retention are the top two priorities for methodology research1. This is not surprising since around 50% of trials fail to achieve their recruitment targets and retention can often be less than 80%.  There is still little evidence available to support the development of effective recruitment and retention strategies2,3. 

Feasibility and pilot work is common before a full-scale trial but there are rarely clear descriptions of recruitment and retention strategies, success/failure thresholds are often absent, nor are there clear assessments of the generalisability limits of feasibility and pilot studies for any future trial. The link between pilot work and successful recruitment and retention remains ambiguous.

The PhD proposal

The PhD proposal is divided into three phases:

  1. Phase 1: Systematic review and meta-synthesis of qualitative research undertaken to improve retention and recruitment to trials at the feasibility stage.  This will provide a framework for trialists regarding the ways qualitative research can help to ensure that recruitment and retention processes are efficient, more transferable to other trials, easier to adapt in light of ongoing recruitment and retention and generally improved.
  2. Phase 2: Stakeholder involvement through surveys and in-depth interviews to explore their experiences of running feasibility studies, particularly with regard to recruitment and retention. Brief questionnaires and semi-structured interviews will be conducted to explore how teamwork influences recruitment and retention in trials.  Participants will be purposefully selected to maximize variation in views and experiences, as well as trial setting, intervention type and disease.  
  3. Phase 3:  Packaging the results of Phases 1 and 2 into a form that trialists and others can easily fit into their work.  In particular, the specification of a new type of document, the recruitment and retention plan, equivalent in status to the statistical analysis plan. These information packages would be evaluated together with trialists and trial team members based at selected UK Trials Units.


  1. Tudor-Smith et al. The trials methodological research agenda: results from a priority setting exercise. Trials 2014; 15:32.
  2. Treweek S et al. Methods to improve recruitment to randomised controlled trials: Cochrane systematic review and meta-analysis. BMJ Open 22013;3: e002360. doi:10.1136/ bmjopen-2012-002360
  3. Brueton et al. Strategies to improve retention in randomised trials. Cochrane Database of Systematic Reviews 2013, Issue 12. Art. No.: MR000032. DOI: 10.1002/14651858.MR000032.pub2.
  4. El Feky A et al. A Protocol for a Systematic Review of Non-Randomised Evaluations of Strategies to Increase Participant Retention to Randomised Controlled Trials Syst Rev. 2018 Feb 20;7(1):30. doi: 10.1186/s13643-018-0696-7.  https://pubmed.ncbi.nlm.nih.gov/29458415/