Operationalizing a model to quantify implementation of a multi-component intervention in a stepped-wedge trial.

Background: It is challenging to interpret the results of multifaceted interventions due to complex program theories that are difficult to measure in a quantifiable manner. The aims of this paper were, first, to develop a model for a comprehensive quantitative implementation evaluation and, second, to operationalize it in the process evaluation of the stepped-wedge cluster randomized controlled trial: "Prevention of low back pain and its consequences among nurses' aides in elderly care" to investigate if implementation differed across intervention components, steps, and settings (workplaces).

Methods: Operationalization of a quantifiable measure of implementation requires three steps: (1) development of a program logic and intervention protocol, (2) description of a complete and acceptable delivery of the intervention, and (3) description of what determines the receipt of the intervention. Program logic from a previously developed multifaceted stepped-wedge intervention was used. The optimal delivery of the intervention was defined as the deliverers' full understanding and following of the intervention protocol and that they performed their best and contributed to the participants' attention and motivation (fidelity). The optimal receipt of the intervention was defined as participants being fully present at all intervention activities (participation), being motivated and satisfied, and having a good social support (responsiveness). Measurements of the fidelity, participation, and responsiveness were obtained from logbooks and questionnaires. Fidelity was multiplied by participation to measure exposure of the intervention to the individual. The implementation was determined from optimal delivery and optimal receipt on a scale from 0 (no implementation) to 100 (full implementation) on individual and organizational level.

Results: Out of 753 sessions, 95% were delivered. The sessions were delivered with 91% success (fidelity) across the organization. Average participation, fidelity, exposure, and responsiveness were 50, 93, 48, and 89% across all participants. The implementation of the intervention was uniform across steps (p = 0.252) and workplaces (p = 0.125) but not for intervention components (p = 0.000). However, participation, fidelity, exposure, and responsiveness varied between workplaces.

Conclusions: This study developed a quantifiable implementation evaluation measuring participation, fidelity, exposure, and responsiveness. The quantifiable implementation evaluation was suitable for comparing implementation across steps, components, and settings and can be applied in the analyses on the impact of implementation of complex interventions.