Adjunctive Interventions in Implementation Research:​ One “thing”? Two things? Old thing? New thing?

Nanette Benbow, MA
Northwestern University

Dennis Li, MPH, PhD
Northwestern University

James Merle, PhD
University of Utah

ABSTRACT:
Implementation science currently groups change methods into two categories: (1) clinical, behavioral, or biomedical interventions targeting recipients’ health outcomes, and (2) implementation strategies—actions taken to improve system-level delivery of an intervention. Differentiating interventions from strategies based on their intended functions is critical to accurately attributing the effects of each change method on its respective health or implementation outcomes. However, in our work coordinating 200+ HIV implementation research projects and conducting systematic reviews of HIV intervention implementation, we identified change methods that had characteristics of both interventions and strategies and were inconsistently classified. To alleviate confusion and improve change method specification, we propose that implementation science should adopt the term adjunctive interventions to classify change methods that fall into this gray area. Adjunctive interventions are distinguished from other change methods by their intended targets, desired outcomes, and theory of action and causal processes. Whereas health interventions target recipients and have a direct, causal effect on the health outcome, adjunctive interventions enhance recipients’ motivation, self-efficacy, or capacity for initiating, adhering to, or engaging with the health intervention and thus have an indirect causal link to the health outcome via increasing the probability of recipients’ utilization of the health intervention. Adjunctive interventions are incapable of directly producing the health outcome and require additional implementation strategies to deliver alongside the health intervention. We will discuss case examples, logic modeling, and considerations for adjunctive intervention research. Conceptualizing adjunctive interventions as a separate type of change method will advance implementation research by improving tests of effectiveness and the specification of mechanisms and outcomes, which will accelerate research evidence to achieve public health impact.