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Fidelity in complex behaviour change interventions: a standardised approach to evaluate intervention integrity
  1. Tom Mars1,
  2. David Ellard2,
  3. Dawn Carnes1,
  4. Kate Homer1,
  5. Martin Underwood3,
  6. Stephanie J C Taylor1
  1. 1Centre for Primary Care and Public Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, London, UK
  2. 2Clinical Trials Unit (T0.10), Warwick Medical School, University of Warwick, Coventry, UK
  3. 3Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, UK
  1. Correspondence to Tom Mars; t.s.mars{at}


Objectives The aim of this study was to (1) demonstrate the development and testing of tools and procedures designed to monitor and assess the integrity of a complex intervention for chronic pain (COping with persistent Pain, Effectiveness Research into Self-management (COPERS) course); and (2) make recommendations based on our experiences.

Design Fidelity assessment of a two-arm randomised controlled trial intervention, assessing the adherence and competence of the facilitators delivering the intervention.

Setting The intervention was delivered in the community in two centres in the UK: one inner city and one a mix of rural and urban locations.

Participants 403 people with chronic musculoskeletal pain were enrolled in the intervention arm and 300 attended the self-management course. Thirty lay and healthcare professionals were trained and 24 delivered the courses (2 per course). We ran 31 courses for up to 16 people per course and all were audio recorded.

Interventions The course was run over three and a half days; facilitators delivered a semistructured manualised course.

Outcomes We designed three measures to evaluate fidelity assessing adherence to the manual, competence and overall impression.

Results We evaluated a random sample of four components from each course (n=122). The evaluation forms were reliable and had good face validity. There were high levels of adherence in the delivery: overall adherence was two (maximum 2, IQR 1.67–2.00), facilitator competence exhibited more variability, and overall competence was 1.5 (maximum 2, IQR 1.25–2.00). Overall impression was three (maximum 4, IQR 2.00–3.00).

Conclusions Monitoring and assessing adherence and competence at the point of intervention delivery can be realised most efficiently by embedding the principles of fidelity measurement within the design stage of complex interventions and the training and assessment of those delivering the intervention. More work is necessary to ensure that more robust systems of fidelity evaluation accompany the growth of complex interventions.

Trial Registration ISRCTN No ISRCTN24426731.

  • Complex Interventions
  • Fidelity
  • Treatment Integrity

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