What is fidelity? A systematic review of provider fidelity and its associations with engagement and outcomes in parenting programs

As developers and practitioners translate parenting interventions from research to practice, significant heterogeneity in provider fidelity and parent engagement with the program has contributed to observed declines in intervention effectiveness. Despite this, empirical investigations of the relationship between provider fidelity, parent engagement, and intervention outcomes are scarce and those that exist show discrepant outcomes. This is, in part, due to the variability in the way fidelity is defined, operationalized, and measured. Therefore, following PRISMA-P guidelines, this review elucidates the relationship between provider fidelity, parent engagement, and intervention outcomes in parenting interventions, with a particular emphasis on how provider fidelity is defined and measured. A systematic search revealed 264 articles, of which 25 met inclusion criteria. As anticipated, results suggest that there are inconsistencies in the relationship between provider fidelity, parent engagement, and intervention outcomes, and these inconsistencies appear related to how fidelity is defined. Across studies, definitions of fidelity were related to one or more dimensions, including adherence, competence/quality, and knowledge, with those measures that captured all three dimensions demonstrating the most consistency in the relation between fidelity and intervention outcomes. Although methodological limitations exist, increased precision in fidelity measurement will have positive implications for the widespread implementation of parenting programs.