When assessing generalisability, focusing on differences in population or setting alone is insufficient.

Area of Science:

• Health Services Research
• Implementation Science
• Program Evaluation

Background:

• Current generalisability assessments in evaluation articles are insufficient for determining intervention applicability in new contexts.
• Existing tools for assessing generalisability are complex and infrequently utilized, hindering practical application.
• There is a need for a novel approach to evaluating intervention generalisability beyond superficial population and setting characteristics.

Discussion:

• Shifting focus from generic characteristics to an intervention's mechanism of action is crucial for understanding its effectiveness.
• Evaluating 'how' or 'why' an intervention works provides deeper insights into its potential for replication.
• This mechanism-focused approach enhances the utility of evaluation research for real-world implementation.

Key Insights:

• Outcome evaluations should integrate programme theory to elucidate causal pathways.
• Process evaluations must prioritize understanding the mechanism of action over merely documenting activities.
• Scoping studies in new settings are essential for adapting identified mechanisms to local contexts.
• Innovative synthesis methods are required to uncover mechanisms of action from existing data, especially when process evaluations are scarce.

Outlook:

• This paradigm shift promises more robust and actionable evidence for intervention scale-up and adaptation.
• Future research should prioritize developing and applying methods that reveal intervention mechanisms.
• Enhanced understanding of mechanisms will improve the reliability and validity of generalisability assessments.