Table 1 Hybrid design characteristics and key challenges as described by Curran [3] and abridged by the authors

Research aims

Primary aim: determine effectiveness of a clinical intervention

Secondary aim: better understand context for implementation

Co-primary aim: determine effectiveness of a clinical intervention

Co-primary aim: determine feasibility and potential utility of an implementation intervention/strategy

Primary aim: determine utility of an implementation intervention/strategy

Secondary aim: assess clinical outcomes associated with implementation trial

Research questions (examples)

Primary question: will a clinical treatment work in this setting among these patients?

Secondary question: what are potential barriers/facilitators to a treatment’s widespread implementation?

Co-primary question: will a clinical treatment work in this setting/these patients?

Co-primary question: does the implementation method show promise (either alone or in comparison with another method) in facilitating implementation of a clinical treatment?

Primary question: which method works better in facilitating implementation of a clinical treatment?

Secondary question: are clinical outcomes acceptable?

Units of randomization

Patient, clinical unit

Clinical effectiveness: see type I

Implementation: see type III, although may be nonrandomized, for example, case study

Provider, clinical unit, facility, system

Comparison conditions

Placebo, treatment as usual, competing treatment

Clinical effectiveness: see type I

Implementation: see type III, although may be nonrandomized, for example, case study

Provider, clinical unit, facility, system: implementation as usual, competing implementation strategy

Sampling frames

Patient: limited restrictions, but some inclusion/exclusion criteria

Provider, clinical unit, facility, system: choose subsample from relevant participants

Patient: limited restrictions, but some inclusion/exclusion criteria. Providers/clinics/facility/systems; consider “optimal” cases

Provider/clinic/facility/system: either “optimal” cases or a more heterogeneous group

Secondary: all or selected patients included in study locations

Program design

Program is largely designed by the research team, but can be informed by program sites

Program is designed collaboratively by researchers and program site and adapted to setting and populations.

Implementation strategies may be designed by the research team, collaboratively by the research team and program site, or by the program site with the research team as consultants and or evaluators.

Program delivery

Program is largely delivered by the research team with attention to fidelity

Delivered by the program site, with support from the research team. Fidelity may be variable, with reasons for variability explored

Delivered by the program site with variable support from the research team. Fidelity may be variable, with reasons for variability explored

Evaluation methods

Primary aim: quantitative, summative

Secondary aim: mixed methods, qualitative, process-oriented

Clinical effectiveness aim: quantitative, summative

Implementation aim: mixed method; quantitative, qualitative; formative and summative

Primary aim: mixed method, quantitative, qualitative, formative, and summative

Secondary aim: quantitative, summative

Measures

Primary aim: patient symptoms and functioning, possibly cost

Secondary aim: feasibility and acceptability of implementing clinical treatment, sustainability potential, barriers and facilitators to implementation

Clinical effectiveness aim: patient symptoms and functioning, possibly cost-effectiveness

Implementation aim: adoption of clinical treatment and fidelity to it, as well as related factors

Primary aim: adoption of clinical treatment and fidelity to it, as well as related factors

Secondary aim: patient symptoms, functioning, services use

Potential design challenges

Generating “buy in” among clinical researchers for implementation aims. Insuring appropriate expertise on study team to conduct rigorous Secondary aim. These studies will likely require more research expertise and personnel, and larger budgets, than non-Hybrids

Generating “buy in” among implementation researchers for clinical intervention aims. These studies will require more research expertise and personnel, as well as larger budgets, than non-Hybrids. Insuring appropriate expertise on study team to rigorously conduct both aims “Creep” of clinical treatment away from fidelity needed for optimal effectiveness. IRB complexities with multiple types of participants

Primary data collection with patients in large, multisite implementation trials can be unfeasible, and studies might need to rely on subsamples of patients, medical record review, and/or administrative data. Patient outcomes data will not be as extensive as in traditional effectiveness trials or even other Hybrid type and might be insufficient to answer some questions. “Creep” of clinical treatment away from fidelity needed for optimal effectiveness. Institution review board complexities with multiple types of participants