Assessing the applicability of findings in systematic reviews of complex interventions can enhance the utility of reviews for decision making.

Assessment of applicability is an essential part of the systematic review process. In the context of systematic reviews of the effects of interventions, applicability is an assessment of whether the findings of a review can be applied in a particular context or population. For more complex interventions, assessing applicability can be challenging because of greater diversity of, and interactions within and between, the intended population, intervention components, comparison conditions, and outcomes as well as a range of further considerations related to intervention context and theoretical basis. We recommend that review authors plan and conduct analyses to explain variations in effect and answer questions about mechanisms of action and influence of different settings, contexts, and populations. We also recommend that review authors provide rich descriptions of the setting, implementation details, resource use, and contexts of included studies and assess applicability for at least one target population, setting, and context. This should facilitate applicability assessments by end users. Consensus on terminology is needed and guidance should be developed for the synthesis of implementation information within reviews as well as the documentation of applicability judgments by review authors.