Objectives: To understand whether interventions are effective, we need to know whether the interventions are delivered as planned (with fidelity) and engaged with. To measure fidelity and engagement effectively, high‐quality measures are needed. We outline a five‐step method which can be used to develop quality measures of fidelity and engagement for complex health interventions. We provide examples from a fidelity study conducted within an evaluation of an intervention aimed to increase independence in dementia. //
Methods: We propose five steps that can be systematically used to develop fidelity checklists for researchers, providers, and participants to measure fidelity and engagement. These steps include the following: (1) reviewing previous measures, (2) analysing intervention components and developing a framework outlining the content of the intervention, (3) developing fidelity checklists and coding guidelines, (4) obtaining feedback about the content and wording of checklists and guidelines, and (5) piloting and refining checklists and coding guidelines to assess and improve reliability. //
Results: Three fidelity checklists that can be used reliably were developed to measure fidelity of and engagement with, the Promoting Independence in Dementia (PRIDE) intervention. As these measures were designed to be used by researchers, providers, and participants, we developed two versions of the checklists: one for participants and one for researchers and providers. //
Conclusions: The five steps that we propose can be used to develop psychometrically robust and implementable measures of fidelity and engagement for complex health interventions that can be used by different target audiences. By considering quality when developing measures, we can be more confident in the interpretation of intervention outcomes drawn from fidelity and engagement studies
