The use of theory in process evaluations conducted alongside randomized trials of implementation interventions: A systematic review

Interventions to implement changes into health care practice (i.e., implementation interventions) are critical to improving care but their effects are poorly understood. Two strategies to better understand intervention effects are conducting process evaluations and using theoretical approaches (i.e., theories, models, frameworks). The extent to which theoretical approaches have been used in process evaluations conducted alongside trials of implementation interventions is unclear. In this study context, we reviewed (a) the proportion of process evaluations citing theoretical approaches, (b) which theoretical approaches were cited, and (c) whether and how theories were used. Systematic review (PROSPERO: CRD42016042789). MEDLINE, PsycINFO, Embase, CINAHL, and Cochrane CENTRAL were searched up to July 31, 2017. For all studies, data extraction included names and types of theoretical approaches cited. For studies citing a theory, data extraction included study characteristics and extent of theory use (i.e., "informed by," "applied," "tested," "built/created" theory). We identified 123 process evaluations. Key findings: (a) 77 (63%) process evaluations cited a theoretical approach; (b) the most cited theory was normalization process theory; (c) 32 (26%) process evaluations used theory: 7 (22%) were informed by, 18 (56%) applied, 7 (22%) tested, and none built/created theory. Although nearly two thirds of process evaluations cited a theoretical approach, only a quarter were informed by, applied, or tested a theory-despite the potential complementarity of these strategies. When theory was used, it was primarily applied. Using theory more substantively in process evaluations may accelerate our understanding of how implementation interventions operate.