Table 4.

Preliminary recommendations for identifying core functions and forms

Steps	Recommendations
Step 1—search for and review existing materials	• Cast a wide net when searching for existing materials—do not limit your search to peer-reviewed literature. Relevant materials may be available as gray literature on program or funder websites. Personal communications with members of the evidence-based intervention (EBI) team are also potential sources of existing materials. • Even if core functions and theory of change are not specified in existing materials, existing materials can prove useful in other ways (i.e., to provide context for the intervention or guide development of primary data collection materials).
Step 2—develop semistructured interview guide	• Review existing materials to inform development of primary data collection materials. • Make sure questions are “participant friendly”: avoid jargon in questions, instead, provide definitions of terms and phrase questions in the context of your specific intervention. ◯ For example: Instead of “ what are the moderators of your intervention?” ask “were there aspects of xxx intervention (or xxx context) that boosted its effectiveness?” • Ask about barriers to the outcome of interest encountered in usual care: this can serve as a jumping off point for the rest of the interview, making it easier for participants to think about the theory of change and primary causal pathway. Information on barriers to change was critical in the analysis phase for specifying the theory of change. • Theory of change: make sure to probe on responses about theory of change. For example, if a participant says “I think the intervention works because it makes clinicians feel comfortable” probe as to why/how it makes clinicians feel comfortable. This will help clearly define the causal pathways. • Core functions: ask about core functions directly, after asking about EBI activities and the theory of change. As a lead-in to the questions focusing on core functions, provide an explanation of what core functions are and why identifying them is important. Again, our explanation avoided jargon and framed core functions as the “active ingredients” or “secret sauce” that drove the success of the intervention. We also found it helpful to ask several questions about core functions and probe often to ensure respondents were drilling down to “the core” of core functions. • Probe often to ensure you are drilling down to the underlying principles of why certain activities were important to the overall success of the intervention. • Consider developing supplemental materials (e.g., short descriptions of the intervention’s activities) to distribute to interview participants.
Step 3—recruit interview participants	• Try to maximize heterogeneity in your sampling frame and final sample by recruiting a variety of roles (research assistant, statistician, and lead developer) from a variety of perspectives (researcher vs. clinician). • Employ snowball sampling to maximize variation in perspectives, especially when one perspective (e.g., researcher and clinician) is overrepresented in the sampling frame.
Step 4—conduct interviews	• Use interviews or other bidirectional methods (e.g., focus groups) to allow for probing and follow-up questions
Step 5—analyze interview data	• Complete analysis in the following order: ◯ Usual care pathway (focusing on barriers to your outcome of interest encountered in usual care) ◯ Theory of change (primary and secondary causal pathways) ◯ Forms (activities) of the intervention ◯ Core functions ◯ Mapping forms (activities) to core functions • Identifying the barriers to outcome of interest encountered in usual care is critical to clearly elucidating the causal pathways in the theory of change. The barriers to change provide a clear “gap” that the primary and secondary causal pathways should (ideally) address • The primary/secondary causal pathways in your theory of change will likely form each core function. With each core function identified, then review all data coded as forms (activities) and discuss whether the activity is related to/operationalizes core function. If so, the activity is related to a core function. If not, it is unrelated.
Step 6—map theory of change onto extant theory from the literature	• Helpful in “validating” the “little-t” theory of change and resulting core functions • To identify a relevant Big-T theory, first consider the type of change your EBI is affecting (e.g., individual level and system level). You may have to explore extant, Big-T theories from other fields outside of implementation science based on the level of change and type of change. For example, person-level change in behavior may point to theories from health behavior or psychology; organizational-level change may point to theories from sociology or organizational theory.