The efficacy implementation ratio: a conceptual model for understanding the impact of implementation strategies using health outcomes

Improved health outcomes are the standard by which the benefit and value of implementation should be judged. Implementation outcomes are typically used to provide important measurements of processes and inputs in implementation science. However, it cannot be assumed that changes in implementation outcomes will always translate to health outcome improvements. Health outcomes are influenced by both the efficacy of treatments as well as how well they are implemented, so determining the success of implementation strategies using health outcomes may be influenced by the efficacy of treatments being integrated to practice. It is important to account for this variation in treatment efficacy when ascertaining the relative contribution of an implementation strategy to improved health outcomes. We propose a conceptual model to illustrate this issue, which considers the success of an implementation strategy, relative to the efficacy of the treatment being implemented, to evaluate the indirect success of implementation strategies on health outcomes. This is observed using an efficacy implementation ratio (EIR), expressed as a ratio of the impact of treatments promoted by an implementation strategy (ab) and that of the treatment in isolation (b): EIR=μabμb. Considering the indirect impact of implementation strategies on health outcomes, relative to the efficacy of implemented treatments provides a potential way to account for variations in treatment efficacy when ascertaining the success, benefits, and value of an implementation strategy in a given context. This paper proposes a novel conceptual model to reason and communicate our argument that the efficacy of treatment needs to be better considered during implementation evaluations.

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