Table 1.

Mapping of the HEAL-D feasibility study research questions, process evaluation data sources and evaluation methods

Process evaluation domain and research questions	Data sources										Evaluation method
	Patient questionnaires	Session observations	Session record of activities	Patient evaluation forms	Educator interviews	Patient interviews	Patient focus groups	Attendance records	HCP interviews	Commissioner interviews
Testing intervention theory and mechanisms of change
Are the intervention’s mechanisms of change operationalised as hypothesised?	X	X	X	X	X	X	X				Qualitative data collected through interviews/focus groups with patients and educators, and session observation notes will be used to evaluate how the theory of the intervention operationalises and interacts with contextual factors.
How is the operationalisation of the mechanisms of change influenced by contextual factors?		X	X		X	X	X
Does the interaction of the mechanisms of change with contextual factors give rise to unintended effects?		X	X		X	X	X
Assessing usual practice and contamination
Is HEAL-D differentiable from ‘usual practice’?						X					Interviews will be conducted with patients from both arms. Experiences of the intervention and control will be explored. With control patients issues of contamination and perceptions of ‘usual care’ will be discussed.
Is there contamination in control patients?						X
Assessing implementation
What is the intervention reach and dose?	X							X			Questionnaire data will assess who receives the intervention and how representative they are, for example, age, gender, ethnicity and working status. Attendance records will be used to quantify the proportion of patients receiving the full versus part intervention.
Are the HEAL-D components/sessions delivered with fidelity and what is the nature of any adaptions?		X	X		X						To assess fidelity and compare intervention deliveries and contextual impacts educators will complete a record of activities and materials and list any resources/activities/discussions that were additional to the standardised schedule. These will be explored in depth in educator interviews that will be conducted at the end of the programme delivery. The research team will observe HEAL-D delivery to quantitatively assess coverage of curriculum, use of supporting materials and behaviour change techniques, quality of delivery and participant engagement (binary score or a 5-point Likert scale). Observers will qualitatively document course adaptations and general contextual observations.
Does the delivery of HEAL-D differ between sites, and what gives rise to differences?		X	X		X
How well are the HEAL-D components/sessions delivered?		X	X
Assessing intervention acceptability
Is HEAL-D acceptable to patients, commissioners and healthcare professionals?		X		X		X	X		X	X	Acceptability will be evaluated through a range of qualitative and quantitative data. Quantitative data will be generated in patient evaluations, which will use 10-point scales to assess their views on the quality of the programme content, structure, format and delivery; the sessions/programme will be deemed ‘acceptable’ where they score ≥6 points. Interviews/focus groups with patients, educators, healthcare professionals and commissioners will explore acceptability through qualitative data, for example, reasons for attendance/non-attendance among patients and suggestions for amendments.
Assessing intervention sustainability
How likely is the HEAL-D intervention to be sustainable and what factors might ensure sustainability?									X	X	Qualitative data collected through interviews with healthcare professionals and commissioners will be used to evaluate barriers and facilitators to implementation of HEAL-D into current care pathways, and its fit with organisational priorities, and the feasibility of sustained resource allocation to the HEAL-D intervention if found to be successful.

HCP, healthcare professionals; HEAL-D, Healthy Eating & Active Lifestyles for Diabetes.