Process Evaluations for the Scale-Up of Complex Interventions - a Scoping Review

Area of Science:

• Public Health
• Health Services Research
• Implementation Science

Background:

• Complex health interventions (CHIs) are integral to public health and social care.
• Process evaluations (PEs) are vital for understanding CHI implementation, mechanisms of change, and contextual influences.
• Scaling up CHIs presents unique challenges due to their complexity and heterogeneity.

Purpose of the Study:

• To describe current practices of conducting PEs during the scale-up of CHIs.
• To identify common themes, methods, and outcomes in PEs accompanying CHI scale-up.
• To inform best practices for process evaluation in health intervention scale-up.

Main Methods:

• A scoping review of the literature was performed.
• Searched eight primary data sources for studies on PEs alongside or after CHI scale-up.
• Extracted data on study and intervention characteristics, PE methods, and stakeholder involvement.

Main Results:

• 56 studies were included from 10,538 records, covering seven thematic areas of CHI scale-up.
• Scale-up specific frameworks were rarely used; PEs commonly focused on context-related barriers/facilitators.
• PE data were often collected "once-off" using mixed methods; scale-up strategies included increasing coverage, comprehensiveness, and institutionalization.

Conclusions:

• Variations in PE conduct during CHI scale-up reflect contextual differences and conceptual challenges.
• A continuous, systems-driven PE approach using mixed methods is ideal for informing real-world adaptations.
• PEs should ideally occur alongside scale-up projects to guide strategy adjustments and understand impact mechanisms.