Disentangling the effects of strategies for guideline implementation in school health services: a hybrid type 2 cluster-randomized factorial trial

Background Translating evidence-based guidelines into actionable improvements and sustained behavior change in practice remains a critical challenge across sectors. Evidence on strategies commonly used to disseminate and implement guidelines is scarce, and studies testing the effects and interactions of discrete and blended strategies are called for. This study disentangled a co-created blended implementation strategy into its more discrete dissemination and implementation strategies: Audit and feedback+, Ongoing consultation, and Dissemination. We examined the individual and interactional effects of these strategies on fidelity to a national guideline for health consultations with 8th -grade students in the Norwegian school health services. Methods A hybrid type 2 cluster-randomized factorial trial was conducted in 25 municipalities and 49 schools. Three dissemination and implementation strategies constituted the experimental factors, resulting in eight experimental conditions representing different combinations of the strategies to which schools were randomized. A total of 56 school nurses conducted consultations with 1400 students. Students and school nurses completed questionnaires at the beginning of the school year and after the 8th -grade consultation. Fidelity to the guideline for 8th -grade consultations was assessed by evaluating adherence to recommendations, the quality of adherence, and consultation duration. Linear mixed effects models were used to examine the effects. Results School nurses and students reported moderate to high guideline fidelity across conditions, and few differential effects were found. Only the Audit and feedback+ strategy had a significant main effect on adherence, which was negative: nurses with Audit and feedback+ addressed fewer guideline-recommended themes during consultations. Conclusions No convincing differential or additive effects of the dissemination and implementation strategies on guideline fidelity were observed, which was generally high. Frequent fidelity measurement may itself have functioned as an implementation strategy, whereas Audit and feedback+ appeared to facilitate prioritization of consultation content without improving consultation quality. Overall, the study points to the importance of parsimony and mechanism-focused evaluation when designing and testing strategies for implementing evidence-based guidelines. Trial registration ISRCTN reg.nr. 24​173​836.