The TANDEM trial: protocol for the process evaluation of a randomised trial of a complex intervention for anxiety and/or depression in people living with chronic obstructive pulmonary disease (COPD).

Background: TANDEM is a randomised controlled trial of a complex healthcare intervention to improve the psychological and physical health of people living with chronic obstructive pulmonary disease (COPD) and anxiety and/or depression. Based on health psychology theory set out in a logic model, respiratory health professionals were recruited and trained to deliver a cognitive behavioural approach intervention (The TANDEM intervention) under the supervision of senior cognitive behavioural practitioners. Here, we describe the protocol for the process evaluation commissioned alongside the trial. A realist approach that includes attention to describing contexts and mechanisms has been adopted.

Methods: We set up a multi-disciplinary team to develop and deliver the process evaluation. The mixed-methods design incorporates quantitative process data; monitoring of intervention fidelity; qualitative interviews with patients, carers, health professionals (facilitators) and clinical supervisors about their perspectives on acceptability of the intervention; and exploration with all stakeholders (including management/policy-makers) on future implementation. Normalisation process theory (NPT) will inform data collection and interpretation with a focus on implementation. Quantitative process data will be analysed descriptively. Qualitative interview data will be analysed before the trial outcomes are known using analytic induction and constant comparison to develop themes. Findings from the different elements will be reported separately and then integrated.

Conclusion: Detailed description and analysis of study processes in a research trial such as TANDEM enables research teams to describe study contexts and mechanisms and to examine the relationship with outcomes. In this way, learning from the trial goes beyond the randomised control trial (RCT) model where effectiveness is prioritised and makes it possible to explore issues arising for post-trial study implementation.

Trial Registration: ISRCTN ISRCTN59537391 . Registered on 20 March 2017. Trial protocol version 6.0, 22 April 2018. Process evaluation protocol version 4.0, 1 November 2020.