Table 2.

Overview of selected frameworks and theories used to shape the process evaluation during scale-up.

RE-AIM	RE-AIM guides the planning and evaluation of programs according to the five key RE-AIM outcomes: Reach (the target population), Effectiveness (the impact on outcomes), Adoption (the extent to which individuals and settings adopt the intervention), Implementation (the fidelity and consistency of delivery), and Maintenance (the sustainability of the intervention over time) [7]. While mostly used in the evaluation stages, the RE-AIM framework can be used in the implementation of complex interventions by guiding its planning, execution and evaluation. In this review, RE-AIM was mostly used to map different outcomes of interest in relation to the scale-up process.
Framework for Reporting Adaptations and Modifications-Enhanced (FRAME) – Implementation Strategies (FRAME-IS)	FRAME or FRAME-IS is designed to guide researchers and practitioners in reporting adaptations and modifications made to interventions or implementation strategies respectively. It emphasizes transparency and clarity in documenting changes to interventions or strategies, ensuring that the rationale and impact of adaptations are clearly communicated [81]. By reporting adaptations and modifications in the original intervention, using this framework adequately provides information on scale-up.
Integrated Promoting Action on Research Implementation in Health Services (i-PARIHS) framework	i-PARIHS helps understand and guide the implementation of evidence-based practices in health services. It considers the interaction between Innovation (the new practice), Recipients (the individuals and teams implementing the practice), Context (the environment in which implementation occurs), and Facilitation (strategies to support implementation) [82]. This framework promotes that the scale-up is tailored to the specific context.
Normalization Process Theory	This classic theory focuses on understanding how new practices, technologies, or interventions become embedded and integrated into routine work in healthcare settings. It explores the processes through which individuals and groups make sense of, engage with, and sustainably incorporate innovations into their everyday practices [83].
(updated) Consolidated Framework for Implementation Research (CFIR)	CFIR helps identify barriers and facilitators to implementation, guides strategy design, and evaluates implementation outcomes. It looks at five main areas: the intervention itself (its attributes and advantages), the external context (like policies and collaborations), the internal organizational setting (culture, leadership), individual characteristics (knowledge, attitudes), and the implementation process (planning, execution, sustainability) [84].
WHO ExpandNet	ExpandNet is a network and approach developed by the World Health Organization (WHO) to support the scale-up of successful health interventions. Key components include: systematic planning, stakeholder engagement, adaptive management, monitoring and evaluation, documentation and knowledge sharing [85].
Non-Adoption, Abandonment, Scale-up, Spread and Sustainability (NASSS) framework	A conceptual implementation framework developed to understand the complexity of implementing and sustaining health interventions or technologies within healthcare systems. It provides a structured approach for analyzing various factors (innovation, individual, adopting organization, wider context, socio-technical system, implementation process, and outcomes over time) that influence the success or failure of implementing innovations in healthcare settings [86].