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Using mixed methods to assess fidelity of delivery and its influencing factors in a complex self-management intervention for people with osteoarthritis and low back pain
  1. Elaine Toomey1,
  2. James Matthews2,
  3. Deirdre A Hurley2
  1. 1 School of Psychology, Arts Millennium Building, National University of Ireland, Galway, Ireland
  2. 2 School of Public Health, Physiotherapy and Sports Science, Health Sciences Centre, University College Dublin, Belfield, Ireland
  1. Correspondence to Dr Elaine Toomey; elaine.toomey{at}


Objectives and design Despite an increasing awareness of the importance of fidelity of delivery within complex behaviour change interventions, it is often poorly assessed. This mixed methods study aimed to establish the fidelity of delivery of a complex self-management intervention and explore the reasons for these findings using a convergent/triangulation design.

Setting Feasibility trial of the Self-management of Osteoarthritis and Low back pain through Activity and Skills (SOLAS) intervention (ISRCTN49875385), delivered in primary care physiotherapy.

Methods and outcomes 60 SOLAS sessions were delivered across seven sites by nine physiotherapists. Fidelity of delivery of prespecified intervention components was evaluated using (1) audio-recordings (n=60), direct observations (n=24) and self-report checklists (n=60) and (2) individual interviews with physiotherapists (n=9). Quantitatively, fidelity scores were calculated using percentage means and SD of components delivered. Associations between fidelity scores and physiotherapist variables were analysed using Spearman's correlations. Interviews were analysed using thematic analysis to explore potential reasons for fidelity scores. Integration of quantitative and qualitative data occurred at an interpretation level using triangulation.

Results Quantitatively, fidelity scores were high for all assessment methods; with self-report (92.7%) consistently higher than direct observations (82.7%) or audio-recordings (81.7%). There was significant variation between physiotherapists’ individual scores (69.8% - 100%). Both qualitative and quantitative data (from physiotherapist variables) found that physiotherapists’ knowledge (Spearman's association at p=0.003) and previous experience (p=0.008) were factors that influenced their fidelity. The qualitative data also postulated participant-level (eg, individual needs) and programme-level factors (eg, resources) as additional elements that influenced fidelity.

Conclusion The intervention was delivered with high fidelity. This study contributes to the limited evidence regarding fidelity assessment methods within complex behaviour change interventions. The findings suggest a combination of quantitative methods is suitable for the assessment of fidelity of delivery. A mixed methods approach provided a more insightful understanding of fidelity and its influencing factors.

Trial registration number ISRCTN49875385; Pre-results.

  • implementation fidelity
  • complex interventions
  • behaviour change

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  • Contributors ET conceptualised and designed the study, conductedthe quantitative data collection and completed the study analysis andinterpretation. JM and DAH provided guidance on the design. DAH is the principal investigator of the SOLAS trial and obtained funding for this study within the trial. All authors provided methodological consultation and were involved in substantial contributions to reviewing of the drafts. All authors approved the final version of the manuscript.

  • Funding This study was funded as part of Health Research Award HRA_HSR/2012/24 by the Health Research Board of Ireland. The funding source had no other involvement in this publication.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval University College Dublin Human Research Ethics Committee (LS-13-54).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Quantitative checklists, the qualitative topic guide and detailed data tables have been provided in the supplementary files. Further information is available if required from the corresponding author at