The case for prioritizing implementation strategy fidelity measurement: benefits and challenges.

Implementation strategies are systematic approaches to improve the uptake and sustainability of evidence-based interventions. They frequently focus on changing provider behavior through the provision of interventions such as training, coaching, and audit-and-feedback. Implementation strategies often impact intermediate behavioral outcomes like provider guideline adherence, in turn improving patient outcomes. Fidelity of implementation strategy delivery is defined as the extent to which an implementation strategy is carried out as it was designed. Implementation strategy fidelity measurement is under-developed and under-reported, with the quality of reporting decreasing over time. Benefits of fidelity measurement include the exploration of the extent to which observed effects are moderated by fidelity, and critical information about Type-III research errors, or the likelihood that null findings result from implementation strategy fidelity failure. Reviews of implementation strategy efficacy often report wide variation across studies, commonly calling for increased implementation strategy fidelity measurement to help explain variations. Despite the methodological benefits of rigorous fidelity measurement, implementation researchers face multi-level challenges and complexities. Challenges include the measurement of a complex variable, multiple data collection modalities with varying precision and costs, and the need for fidelity measurement to change in-step with adaptations. In this position paper, we weigh these costs and benefits and ultimately contend that implementation strategy fidelity measurement and reporting should be improved in trials of implementation strategies. We offer pragmatic solutions for researchers to make immediate improvements like the use of mixed methods or innovative data collection and analysis techniques, the inclusion of implementation strategy fidelity assessment in reporting guidelines, and the staged development of fidelity tools across the evolution of an implementation strategy. We also call for additional research into the barriers and facilitators of implementation strategy fidelity measurement to further clarify the best path forward.