Background: Treatment fidelity has previously been defined as the degree to which a treatment or intervention is delivered to participants as intended. Underreporting of fidelity in primary care randomised controlled trials (RCTs) of complex interventions reduces our confidence that findings are due to the treatment or intervention being investigated, rather than unknown confounders.
Aim: We aimed to investigate treatment fidelity (for the purpose of this paper, hereafter referred to as intervention fidelity), of an educational intervention delivered to general practice teams and designed to improve the primary care management of insomnia.
Method: We conducted telephone interviews with patients and practitioners participating in the intervention arm of the trial to explore trial fidelity. Qualitative analysis was undertaken using constant comparison and a priori themes (categories): 'adherence to the delivery of the intervention', 'patients received and understood intervention' and 'patient enactment'.
Results: If the intervention protocol was not adhered to by the practitioner then patient receipt, understanding and enactment levels were reduced. Recruitment difficulties in terms of the gap between initially being recruited into the study and attending an intervention consultation also reduced the effectiveness of the intervention. Patient attributes such as motivation to learn and engage contributed to the success of the uptake of the intervention.
Conclusion: Qualitative methods using brief telephone interviews are an effective way of collecting the depth of data required to assess intervention fidelity. Intervention fidelity monitoring should be an important element of definitive trial design.
Trial registration: ClinicalTrials. gov id isrctn 55001433 - www.controlled-trials.com/isrctn55001433.