Fidelity of primary care nurses’ delivery of a behaviour change intervention to enhance physical activity in chronic patients

Background The effectiveness of a nurse-led intervention to enhance physical activity, the Activate intervention, was evaluated in primary care patients at risk for cardiovascular diseases in a cluster-randomised controlled trial (n = 195 patients, 31 general practices). To contribute to an accurate interpretation of the trial results, understanding of how the intervention works and enabling reproducibility, this study aimed to evaluate the fidelity of delivery of the Activate intervention by assessing: 1. self-reported fidelity of delivery; 2. observed fidelity of delivery; 3. quality of nurses’ delivery of the Activate intervention and 4. nurses’ beliefs about their capability, motivation, confidence and effectiveness towards delivering the Activate intervention, including behaviour change techniques. Methods An observational study was conducted. Nurses’ self-reported fidelity was evaluated using checklists (n = 279), and the observed fidelity and quality of delivery were examined using audio-recordings of intervention consultations (n = 44). Nurses’ beliefs towards delivering the intervention were assessed using questionnaires (n = 72). Results The self-reported fidelity was 87.6% and observed fidelity was 85.6%, representing high fidelity. The observed fidelity of applied behaviour change techniques was moderate (76.8%). The observed quality of delivery was sufficient and varied among nurses (mean 2.9; SD 4.4; range 0–4). Nurses’ beliefs about their capability, motivation, confidence and effectiveness towards delivering the intervention increased during the trial. Conclusions Nurses delivered most intervention components as intended with sufficient quality. Nurses believed they were capable, motivated and confident to deliver the intervention. They believed the intervention was effective to increase patients’ physical activity level. Despite the high fidelity and moderate fidelity of applied behaviour change techniques, the varying quality of delivery within and across nurses might have diluted the effectiveness of the Activate intervention. Trial registration: ClinicalTrials.gov NCT02725203 registered 31 March, 2016, https://clinicaltrials.gov/ct2/show/NCT02725203.