Learning from scale-up: a qualitative study of scaling-up interventions for people with multiple long-term conditions in primary care

BACKGROUND: Scaling innovations for people living with multiple long-term conditions (MLTCs or multimorbidity) remains challenging, particularly in primary care where organisational capacity, infrastructure, and local contexts vary widely. There is limited empirical understanding of the implementation work needed to navigate these contextual influences when scaling complex innovations across diverse settings. This study aimed to identify and explain the contextual conditions and adaptive implementation strategies that enabled or constrained scale-up of interventions for people with MLTCs in English primary care. METHODS: We conducted a theory-informed qualitative evaluation of four national projects that aimed to scale evidence-based interventions to improve the care of people with MLTCs in primary care. Projects ran between 2021 and 2024. Data included longitudinal interviews with project teams, document analysis, and a stakeholder workshop. Analysis was informed by the Consolidated Framework for Implementation Research (CFIR). RESULTS: Four key themes were identified: (1) Scaling requires relational infrastructure: relationships, trust, and relational continuity were central to gaining traction; (2) Supporting organisations and networks facilitate spread; (3) Engaging primary care practices depends on addressing uneven readiness for research and innovation; and (4) Local intelligence supports implementation at scale. CONCLUSION: Scaling MLTC innovations in primary care is shaped by relational, organisational, and infrastructural factors, including uneven readiness for implementation. Scaling proven interventions requires technical support and investment in the people, relationships, and local infrastructures that support embedding across diverse primary care contexts.