Inside the black box: Refining programme theory in the PriDem dementia care study.

introductionRefining programme theory following feasibility testing is a critical but rarely reported step in the development of complex interventions, creating a 'black box' in implementation science. This lack of transparency limits understanding of how and why interventions work and constrains effective scale-up and adaptation. This challenge is particularly salient in post-diagnostic dementia support, which is often fragmented in primary care, with limited guidance on how system-level interventions can be implemented and adapted in real-world settings. The PriDem programme developed a flexible, primary care-led intervention to improve post-diagnostic dementia support, involving Clinical Dementia Leads (CDLs) working with general practices to strengthen care systems. Programme theory was articulated in a logic model, to guide a feasibility implementation study, which demonstrated intervention feasibility, acceptability, and potential for systems-level change. Understanding how the intervention operated in practice was critical to refining this theory and informing future scale-up. This paper presents a structured exemplar of theory refinement, addressing this recognised gap in implementation science.

methodsA deductive thematic analysis was conducted, using the logic model as a coding framework. We synthesised previously reported findings with new qualitative insights from feasibility interviews, fieldnotes, supervision records and researcher reflections. Confirmed, refined, and newly emergent theoretical components were identified and the logic model updated.

resultsMany original theory elements were confirmed, including improved review processes leading to enhanced care plan personalisation and staff training increasing confidence in care delivery. New mechanisms were identified, such as mapping local services as a relational tool and dementia review templates as educational resources. Pre-implementation activities, such as specific CDL training and champion identification, emerged as critical to success. Role ambiguity and capacity concerns acted as negative mechanisms, impeding implementation. These insights informed a revised logic model to guide future scale-up.

conclusionsThis paper demonstrates the value of theory refinement following feasibility testing. By unpacking the 'black box' of implementation, we offer a transparent model for optimising complex interventions in primary care-led dementia support. TRIAL REGISTRATION NUMBER: ISRCTN11677384.