Protocol for the mixed-methods process and context evaluation of the

introductionTuberculosis (TB) remains a significant public health problem in South Asia. Tobacco use increases the risks of TB infection and TB progression. The METHODS AND ANALYSIS: We are conducting a mixed-methods process and context evaluation informed by an intervention logic model that draws on the UK Medical Research Council's Process Evaluation Guidance. Our approach includes quantitative and qualitative data collection on context, recruitment, reach, dose delivered, dose received and fidelity. Quantitative data include patient characteristics, reach of recruitment among eligible patients, routine trial data on dose delivered and dose received, and a COM-B ('capability', 'opportunity', 'motivation' and 'behaviour') questionnaire filled in by participating health workers. Qualitative data include semistructured interviews with TB health workers and patients, and with policy-makers at district and central levels in each country. Interviews will be analysed using the framework approach. The behavioural intervention delivery is audio recorded and assessed using a predefined fidelity coding index based on behavioural change technique taxonomy. ETHICS AND DISSEMINATION: The study complies with the guidelines of the Declaration of Helsinki. Ethics approval for the study and process evaluation was granted by the University of Leeds (qualitative components), University of York (trial data and fidelity assessment), Bangladesh Medical Research Council and Bangladesh Drug Administration (trial data and qualitative components) and Pakistan Medical Research Council (trial data and qualitative components). Results of this research will be disseminated through reports to stakeholders and peer-reviewed publications and conference presentations. TRIAL REGISTRATION NUMBER: ISRCTN43811467; Pre-results.