Table 1 Analysis of fidelity, feasibility and acceptability of the DiAlert intervention

Fidelity measures

Checklists

Coverage of the role of the trainer and the participants

Checklist coverage: yes/no tick box

Observations with checklists showed that all modules were delivered. The role of the trainer and the objectives for participants were covered.

-during the intervention sessions(Observers)

Evaluations

Engagement of participants

Observations

Engagement was high, demonstrated by active questioning by participants, active participation at the calorie games, most participants completing the homework assignment and attendance in both group sessions.

-after each group session (Observers and Trainer)

Attrition was low: one participant was absent at the second session.

Empowerment philosophy

Observations

The trainer supports the empowerment philosophy during both sessions, see checklist for items of empowerment.

Quotes of participants written down on flip-over sheets

Do relatives of T2DM patients have:

Quotes of participants

Participants have worries about:

1. Relatives (for example ‘worries about my mom/dad/ children’

2. Own health: (for example, ‘I’m afraid of getting diabetes myself’; ‘I think I’m too young to get it [diabetes]!’

-during the first session (Trainer)

1. worries?

2. questions?

Quotes of participants

Main themes of burning questions:

1. Diabetes causality and its relation to lifestyle (for example, ‘What is the primary cause of T2DM? Does stress affect development of T2DM’, ‘How important is eating healthy food, and what is considered to be healthy?’)

2. Questions about diabetes treatment and complications (for example, ‘Why do some people receive pills and others insulin treatment?’, ‘How can someone prevent getting polyneuropathy?’).

3. interests in relation diabetes prevention?

Quotes of participants

Categories of reasons to participate:

1. Risk awareness and worry (for example ‘My risk of getting diabetes is high’)

2. Information seeking (for example, ‘How are lifestyle and diabetes risk related?’)

3. Motivation (for example, ‘Stimulates me to improve my exercise behavior’).

Questionnaire

- perceptions of worry[13]

1 = totally not worried

No significant changes for worry about personal risk and personal control of developing T2DM, for example:

-at baseline

7 = very worried

Indicate your feelings when thinking about chance of getting diabetes: baseline 5.0 ± 1.6; follow-up 5.0 ± 1.6; P = 0.92)

−4 weeks follow-up (Participant)

- personal control[13]

1 = totally disagree

No significant changes for personal control of developing T2DM, for example:

5 = totally agree

I think I have little influence on getting T2DM: baseline 2.5 ± 1.1; follow-up 1.9 ± 1.0; P = 0.08

I can reduce my risk of getting diabetes: baseline 4.3 ± 0.7; follow-up 4.3 ± 1.2; P = 0.92

I think I have little control over my own health: baseline 1.8 ± 0.7; follow-up 1.8 ± 0.7; P = 0.85

- perceived consequences of T2DM[13]

1 = totally disagree

Significant increase of perceived consequences of getting T2DM, for example:

5 = totally agree

Major implications for life: baseline 4.2 ± 0.8; follow-up 4.5 ± 0.7; P = 0.04

Major financial implications^a: baseline 2.9 ± 1.1; follow-up 3.4 ± 1.0; P <0.01

Feasibility measures

Questionnaire

- which recruitment strategies were appropriate / How did participants knew about the study?

Multiple choice including 1 open-ended option.

Recruitment through flyers and advertisements n = 14 (66%), announcement on internet n = 3 (14.4%) and via a relative n = 3 (14.4%)

-at baseline (Participant)

Observations

- time, duration of the modules/sessions

Minutes per module reported on checklist

All modules were delivered within 2 × 150 minutes; duration of modules deviated sometimes from planned time.

-during the intervention sessions (Observer)

Questionnaire

- length of sessions was good:

1 = totally disagree

90% of the participants evaluated the length of the sessions ‘good’ score ≥3

-follow-up 4  weeks (Participant)

4 = totally agree

Evaluation form

- group size

Multiple choice: too small, just right, too large

All participants evaluated the group size ‘just right’

-at the end of second session (Participant)

Acceptability measures

Evaluation form

- generic grade for total intervention: (mean ± SD)

1 (lowest grade)

8.0 ± 1.0

-at the end of second session (Participant)

10 (highest grade)

- usefulness of the separate modules (mean ± SD)

1 = very useful

Introduction 1.5 ±0.5; Risk factors 1.3 ±0.5; Development of diabetes 1.3 ±0.6; Homework 1.8 ±0.9; Information about physical activity 1.4 ±0.5; Information about diet 1.5 ±0.8; Action plan 1.7 ±0.8; Questions 1.5 ±0.7

5 = totally not useful

Questionnaire

- participants manual: instructive and clear

1 = totally disagree

Instructive 3.4 ±0.5; clear 3.4 ±0.5

-follow-up 4  weeks (Participant)

4 = totally agree

- action plan: managed to make one and useful

1 = totally disagree

Managed to make an action plan 2.8 ±0.5; useful to create a personal action plan 3.1 ±0.6

4 = totally agree

(mean ± SD)