^{1}

^{*}

^{1}

^{2}

^{†}

^{3}

^{4}

^{†}

^{1}

^{2}

^{3}

^{4}

Edited by: Marcelo Demarzo, Federal University of São Paulo, Brazil

Reviewed by: Russell E. Glasgow, University of Colorado Hospital, United States; Ana A. Baumann, Washington University in St. Louis, United States

This article was submitted to Public Health Education and Promotion, a section of the journal Frontiers in Public Health

†Co-first authors

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Successful implementation reflects the interplay between intervention, implementation strategy, and context. Hybrid effectiveness-implementation studies allow investigators to assess the effects of both intervention and implementation strategy, though the role of context as a third independent variable (IV) is incompletely specified. Our objective is to expand the hybrid typology to include mixtures of all three types of IVs: intervention, implementation strategy, and context. We propose to use

Successful implementation reflects the complex interplay between intervention, implementation strategy, and context (

Contextual determinants operate at multiple stages and across multiple levels to promote or inhibit intervention and implementation strategy effectiveness (

Hybrid studies offer a platform for the combined assessment of two or more kinds of independent variables. In their seminal article, Curran et al. (

Current and expanded hybrid typologies for implementation research. Gray shading represents study types where the assessment of implementation strategies is a primary or secondary aim. Gray text indicates study types that are currently under- or unspecified. Individual types of three-variable hybrids have been excluded for simplicity. *Curran et al. (

Our objective is to expand on the Curran et al. (

Our expanded typology builds naturally on the idea of hybrid effectiveness-implementation studies by allowing for hybrids of any combination of the three independent variables (IVs):

We propose to use

The expanded typology specifies nine two-variable hybrid studies:

Two-variable hybrid types that include assessment of implementation strategy.

^{*} |
||||||
---|---|---|---|---|---|---|

What is being varied? | Intervention | Intervention and implementation strategy | Implementation strategy | Implementation strategy | Implementation strategy and context | Context |

Research aims | Primary aim: Evaluate intervention effectiveness | Co-primary aim: Evaluate intervention effectiveness | Primary aim: Evaluate implementation strategy effectiveness | Primary aim: Evaluate implementation strategy effectiveness | Co-primary aim: Evaluate implementation strategy effectiveness | Primary aim: Evaluate effects of context |

Secondary aim: Assess implementation outcomes associated with implementation strategy | Co-primary aim: Evaluate implementation strategy effectiveness | Secondary aim: Assess patient health outcomes associated with intervention | Secondary aim: Better understand the context for implementation | Co-primary aim: Evaluate effects of context | Secondary aim: Assess implementation outcomes associated with implementation strategy | |

Research questions (examples) | Primary question: Will the intervention improve health outcomes? | Co-primary question: Will the intervention improve health outcomes? | Primary question: Will the implementation strategy improve implementation outcomes? | Primary question: Will the implementation strategy improve implementation outcomes? | Co-primary question: Will the implementation strategy improve implementation outcomes? | Primary question: Which contextual factors mediate or moderate the effectiveness of the implementation strategy? |

Secondary question: What are the implementation outcomes of the specified implementation strategy? | Co-primary question: Will the implementation strategy improve implementation outcomes? | Secondary question: Are patient health outcomes acceptable? | Secondary question(s): What are the barriers to and facilitators of implementation of the implementation strategy? | Co-primary question: Which contextual factors mediate or moderate the effectiveness of the implementation strategy? | Secondary question: What are the implementation outcomes of the specified implementation strategy? | |

Evaluation methods | Primary aim: Quantitative evaluation of causal effects of intervention | Co-primary aim: Quantitative evaluation of causal effects of intervention | Primary aim: Quantitative evaluation of causal effects of implementation strategy | Primary aim: Quantitative evaluation of causal effects of implementation strategy | Co-primary aim: Quantitative evaluation of causal effects of implementation strategy | Primary aim: Quantitative evaluation of causal effects of context |

Secondary aim: Quantitative, qualitative, or mixed-methods evaluation of implementation outcomes | Co-primary aim: Quantitative evaluation of causal effects of implementation strategy | Secondary aim: Quantitative assessment of patient health outcomes | Secondary aim: Qualitative or mixed-methods process evaluation | Co-primary aim: Quantitative evaluation of causal effects of context | Secondary aim: Quantitative, qualitative, or mixed-methods evaluation of implementation outcomes |

An

An

An

Finally, a

For all two-variable hybrid types proposed here, we assume that there are minimal risks associated with the intervention, the implementation strategy, and the context. Additional recommended conditions include the following.

The expanded typology specifies seven three-variable hybrid studies.

The aims and research questions associated with these three-variable hybrid types follow from the two-variable types described above. For example, an

Though three-variable hybrid types are more complex than two-variable types, we argue that many studies—including some currently denoted as hybrid

We propose an expanded typology of hybrid studies for implementation research that explicitly incorporates mixtures of three IVs: intervention, implementation strategy, and context. This proposal builds from the typology proposed by Curran et al. (

Key implications of expanded hybrid typology.

We propose an Our expanded typology recognizes Investigators should consider intentionally varying context in order to identify and explain the Investigators should consider rigorous |

We believe that the gold standard study design will vary for each hybrid type. Note that we use the phrase

The under-specification of context as an IV in implementation research is reflected in the fact that over three-fourths of the protocols published in the field's leading journal from 2006 to 2017 have been randomized trials (

We have highlighted the implementation strategy IV as it is currently the predominant focus in the field. However, we believe that all three IVs are critical to advancing implementation science. Prototypical implementation studies that evaluate the effectiveness of an implementation strategy, in isolation from its context, risk perpetuating the persistent gap between evidence and practice: they do not generate context-specific knowledge around implementation, scale-up, and de-implementation. Therefore, we argue that, at minimum, implementation strategy effectiveness studies should include a secondary aim related to collecting data on contextual determinants. Ideally, many would go further and systematically test variations in context and measure moderation and mediation of implementation strategy effectiveness. Results from such studies would arm future implementers with valuable information about precisely how to choose and tailor interventions and implementation strategies to match—and benefit from—their particular contexts.

We propose an expanded and renamed typology of hybrid studies for implementation research. Our aims were to formally recognize the role of context as a potential IV, to provide a nomenclature for existing studies aiming to identify the contextual moderators and mediators of intervention and implementation strategy effectiveness, and to motivate future growth in this critical area. We believe all implementation studies should consider a hybrid approach and carefully consider whether context may be an IV of interest.

All authors contributed equally to the conceptualization and drafting of this manuscript, and approved it for publication.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

We would like to thank Geoffrey Curran and Bryan Weiner for their valuable comments on this manuscript. The publication of this manuscript was supported by the University of Washington Implementation Science Program.

The Supplementary Material for this article can be found online at:

Description of data: description of all proposed two-variable and three-variable hybrid study types.

Description of data: examples of