The CHESS trial: protocol for the process evaluation of a randomised trial of an education and self-management intervention for people with chronic headache

BACKGROUND: Process evaluation is increasingly common alongside complex randomised controlled trials (RCTs). This evaluation helps in understanding the mechanisms of impact and how the study processes were executed, and it includes any contextual factors which may have implications for the trial results and any future implementation. This process evaluation is for the Chronic Headache Education and Self-management Study (CHESS) RCT, which is evaluating an education and self-management group behavioural intervention for people with chronic headache. Chronic headache is defined as headaches which are present for 15 or more days per month. The most common types are chronic migraine and chronic tension type and medication overuse headaches. METHODS: We will use a mixed methods approach. Quantitative data will be taken from routine trial data which will help us to assess the reach of the study; i.e. did we reach those whom we expected and from where? Intervention attendance (dose received) and attrition and qualitative data will augment our understanding about reasons why people may not wish to take part in or failed to attend sessions. Interviews with intervention facilitators and trial participants will gain different perspectives on taking part in the trial. Fidelity will be assessed through listening to audio recordings for adherence to course content and competence of the facilitation of a sample of sessions. DISCUSSION: Our process evaluation will allow us to gain insight into how the trial was delivered, the obstacles and enablers encountered and the possible reasons why the interventions may or may not be effective. TRIAL REGISTRATION: ISRCTN79708100. Registered on 16 December 2015. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-019-3372-x) contains supplementary material, which is available to authorized users.