Table 1.

Inclusion and exclusion criteria. *The eligibility criteria for process evaluations are based on the MRC guidance for the process evaluation of complex health interventions [2].

CRITERIA	SCALE-UP	COMPLEX HEALTH INTERVENTION (CHI)	PROCESS EVALUATION (PE)*
Inclusion	Explicitly state that the aim or objective of the study was related to the scale-up of a health care intervention (e.g., integrated care package for Diabetes and Hypertension, exercise-based rehabilitation). The language used by the study authors was central in assessing this criterion.	The intervention of interest was complex. Herein, we follow the description as provided by the UK Medical Research Council, “An intervention might be considered complex because of properties of the intervention itself, such as the number of components involved; the range of behaviours targeted; expertise and skills required by those delivering and receiving the intervention; the number of groups, settings, or levels targeted; or the permitted level of flexibility of the intervention or its components.” [2];	1) The PE entails qualitative and/or quantitative primary research. 2) Only studies that conducted a PE while scaling up and evaluation of the scale-up process itself were included. 3) Explicitly state that a PE was conducted as part of the research study. The nature of these PEs was the subject of this review, and hence, a priori framework or definition was not outlined for these evaluations as such. Therefore, the following criteria were developed. The full text suggested that the study: a) Aimed to conduct a PE in relation to the scale-up of a CHI, or b) conducted implementation research to evaluate structures, resources, and processes in relation to the scale-up of a CHI, or c) evaluated how the scale-up of a CHI produced impact in relation to the scale-up of a CHI, or d) evaluated local context in relation to scale-up of a CHI, or e) a PE was conducted alongside post-evaluation in relation to the scale-up of a CHI.
Exclusion	– Studies not reporting primary research findings (e.g., systematic reviews, editorials, conference proceedings) – Studies in which a PE was conducted to inform future scale-up, rather following or along-side a scale-up process.