Table 1.

COmponents & Rationales for Effectiveness (CORE) Fidelity Method: Development and Case Example with RIT

Stage	Activity	Activity scope	Illustrative case example: Reciprocal Imitation Teaching (RIT) for social communication
1. Gather information	Review published literature	• Conceptual literature (e.g., fidelity, adaptation, theory of change) • Empirical literature (e.g., prior efficacy studies, related interventions)	We reviewed literature on adaptation, theory of change, prior efficacy and effectiveness studies of RIT, and studies of other NDBIs.
	Review “grey literature”	• Unpublished studies (e.g., conference proceedings) • Intervention materials (e.g., manuals, handouts, fidelity tools)	For RIT, we reviewed the following: • Intervention manuals (previous and current) • Provider training slide deck & handouts • Parent training lesson plans and handouts • Current fidelity measurement forms
	Interview recognized experts	• Intervention developers, independent implementers, trainers, and clinicians	We interviewed lead investigators, including RIT developers and experts in other NDBIs.
2. Synthesize information	Describe consistencies & variations across intervention iterations	• Across studies (e.g., adaptations) • Within studies (e.g., different descriptions of what is required versus recommended for fidelity)	We noted variations across studies in the length of training sessions and the amount of recommended practice and delivery. • There were within-study variations between parent and provider manuals (which encourage certain strategies) and fidelity checklists (which frame them as mandatory).
	Conceptualize key distinctions in the structure of the intervention	• Intervention levels (e.g., trainer to therapist, to parent, to child) • Critical strategies (i.e., intrinsic to the intervention as defined) • Modular components (i.e., could be implemented independently)	We considered the following to be important for our conceptualization of key RIT components: • The multi-level nature of RIT as a parent-implemented intervention • Adherence vs. competence in delivering essential practices • Function vs. specifying form when necessary • Elements as mandatory, recommended, or conditional
	Record empirical or hypothesized causal explanations of efficacy	• RCTs, small-n designs, evaluations of treatment mechanisms • Published causal models and experts’ beliefs about how the intervention works	We identified efficacy studies of RIT and searched for evidence of treatment mediation effects for similar NDBIs. We identified prior theory underlying RIT and NDBIs and recorded experts’ explicit causal hypotheses.
3. Finalize CORE model	Work towards consensus among intervention experts and stakeholders	• Preliminary discussion • Intentional consensus process • Additional learning cycles as necessary to reach consensus	We used Nominal Group Technique (NGT) and invited both RIT developers and expert trainers/clinicians to contribute their research and clinical insights on potential key components and their hypothesized causal explanations.
	Document essential intervention components (Components)	• All intervention elements hypothesized as necessary for causal effects	Examples from RIT CORE model: • Contingently imitate child toy play, body movements, gestures, and vocalizations. • Model an action for the child to imitate—so that the child can see it—after a period of contingent imitation. • Pacing of the RIT cycle: spend more time on imitation than on asking the child to imitate.
	Document hypothesized causal explanations (Rationale for Effectiveness)	• Primary and alternative hypotheses of causal effect	Example from RIT CORE model: • Component: Describe the child’s and your play/actions using simple, follow-in language • Rationale for effectiveness: Increases the child’s attention to the imitation model/action and provides appropriate language models. Promotes language.
	Use CORE Fidelity Method in ongoing efficacy studies and implementation efforts	A plan for how to prevent drift or unhelpful adaptations by: • Assessing fidelity • Ensuring fidelity when drafting new documents • Analyzing treatment mechanisms	We initiated a study committee to review new documents (e.g., provider handouts) and initiatives (e.g., plan to analyze mechanism) and compare them to the CORE model as documented.