The CONSIDER Intervention Fidelity Framework for Complex Interventions in Healthcare: A “Best-Fit” Framework Synthesis

Background The focus of clinical trials is typically interventions’ efficacy, or whether they attain their desired outcomes. Comparatively less attention is focused on understanding how or why interventions succeed, or fail to attain, those outcomes. This may be particularly important in trials of complex interventions such as surgery or physiotherapy, which are multifaceted and often tailored to individual participants, providers, or settings, increasing the potential for variations in intervention delivery and effects. The correspondence between the intervention that was planned and what was actually delivered in a trial is the intervention’s fidelity. Several benefits for high levels of intervention fidelity have been proposed. However, a lack of a uniform definition for fidelity and its key components may hinder intervention delivery in clinical trials and the translation of evidence-based interventions to clinical practice.