Fidelity of primary care nurses' delivery of a behavioural change intervention enhancing physical activity in patients at risk of cardiovascular disease: an observational study.

Objective: To evaluate the fidelity of delivery of a nurse-led intervention to enhance physical activity in patients at risk for cardiovascular diseases, the Activate intervention, by assessing: (1) self-reported fidelity of delivery; (2) observed fidelity of delivery; (3) quality of delivery of the Activate intervention and (4) nurses' beliefs about their capability, motivation, confidence and effectiveness towards delivering the Activate intervention, including behavioural change techniques.

Design: An observational study.

Setting: General practices in the Netherlands.

Participants: Primary care nurses (n=20) from 16 general practices.

Primary And Secondary Outcome Measures: Nurses' self-reported fidelity was evaluated using checklists (n=282), and the observed fidelity and quality of delivery were examined using audiorecordings of consultations of the delivery of the Activate intervention (n=42). Nurses' beliefs towards delivering the intervention were assessed using questionnaires (n=72).

Results: The self-reported fidelity was 88.1% and observed fidelity was 85.4%, representing high fidelity. The observed fidelity of applied behavioural change techniques was moderate (75.0%). 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 over time.

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 behavioural change techniques, the varying quality of delivery within and across nurses might have diluted the effectiveness of the Activate intervention.

Trial Registration Number: NCT02725203.