Development and description of a theory-driven, evidence-based, complex intervention to improve adherence to treatment for tuberculosis in the UK: the IMPACT study

Background: Tuberculosis (TB) has a significant treatment burden for patients, requiring at least six months of anti-TB treatment (ATT) with multiple medicines. Ensuring good adherence to ATT is central to global TB strategies, including those in high-income, low-TB incidence (HILI) settings. For adherence interventions to be successful and deliverable, they need to address the personal and environmental factors influencing patient and provider behaviour. Purpose: This paper describes the application of theory and research evidence to inform the design process of the IMPACT manualised intervention to support ATT adherence for adults with TB disease in the United Kingdom (UK). It also provides a full description of the resulting intervention. Methods: We synthesised findings from our formative research (qualitative and quantitative scoping reviews and patient and carer interviews) and supplemented these with clinic observations, a literature review, and healthcare provider interviews. Findings were mapped to the guiding theoretical framework (Perceptions and Practicalities Approach) which was operationalised to design the intervention components and content. An Intervention Development Group (IDG) of relevant stakeholders were consulted to adapt the intervention to local clinical settings. Results: The pragmatic, deliverable components and content for the IMPACT intervention included: (1) an enhanced, structured, risk assessment to systematically identify risk factors for non-adherence plus locally-adapted guidance to mitigate these; and (2) patient educational materials (an animated video and interactive patient booklet) about TB and its treatment, to communicate the need for treatment and address common concerns. Conclusions: Using a theory– and evidence– based approach incorporating stakeholder input, we have developed a multi-component, pragmatic, manualised intervention, which addresses patients’ personal barriers to adherence within local service resources to improve adherence to ATT within UK TB services.