Table 2 Description of questionnaires

Summary of Diabetes Self-Care Activities Measure (SDSCA) [34]

11 Items assessing several aspects of the diabetes regimen: diet, exercise, blood glucose testing, foot care and smoking. Items measure how many days a patient has performed self-care activities in the last 7 days.

10 Items rated on an 8-point Likert scale, measuring how many days an activity is performed in the last week. One item measures smoking status (yes/no) and the amount of cigarettes smoked in the last week. Each of the domains is measured separately.

T0, T6

Food habits questionnaire (FFQ) [35]

18 Items assessing patient’s habits with regard to preparation of food, fatty food intake, dietary products and fruit and vegetable intake.

All items differ in the scoring ranges, varying from four scoring options (never, sometimes, frequently or always) to eight options (never to 7 days a week)

T0, T6

International Physical Activity Questionnaire (IPAQ) [36]

25 Items assessing how many days physical activities are performed during the past 7 days in four domains (work, transportation, housework and leisure-time), 2 items assess sedentary behaviour.

Total physical activity score is calculated as the sum of the number of minutes of total moderate activity for each subdomain, plus two times the number of minutes of total vigorous activity for each subdomain.

T0, T6

EQ-5D-5 L [37]

Quality of life questionnaire.

The classification system (EQ-5D-Profile) covers mobility, self-care, daily activities, pain/discomfort and anxiety/depression. The Visual Analogue Scale (EQ-5D-VAS) is a graduated, vertical line, anchored at 0 (worst imaginable health state) and 100 (best imaginable health state).

For the EQ-5D-Profile each domain has five levels of functioning: from no problems to severe problems.

For the EQ-5D-VAS the patient is asked to rate his/her health by marking a point on the EQ-5D-VAS that best reflects his/her actual health state.

T0, T3, T6, T9^a

The Short Form (36) Health Survey (SF-36) [38, 39]

Generates a profile of scores on eight dimensions of health status: Physical Functioning (10 items), Role Physical (4 items), Bodily Pain (2 items), General Health (6 items), Vitality (4 items), Social Functioning (2 items), Role-Emotional (3 items) and Mental Health (5 items).

The different scales can be summarized in two component scores: the Physical Component Score and the Mental Component Score. Both scores range from 0 (least favorable health state) to 100 (most favorable health state).

T0, T6

The Audit of Diabetes-Dependent Quality of Life (ADDQoL) [40]

A measure of impact and importance of diabetes and its treatment on quality of life. The ADDQoL consists of 19 diabetes-specific items and two overview items. For each item the patient is asked how things would be without diabetes, with an impact rating and an importance rating.

The impact rating ranges from − 3 (very much better) to 1 (worse), the importance rating ranges from 3 (very important) to 0 (not at all important). The average weighted impact ADDQoL score is the sum of all the weighted impact scores in the nominator and of the number of domains in the denominator, and ranges from − 9 to 3.

T0, T6

Diabetes Treatment Satisfaction Questionnaire (DTSQ) [41]

Includes 8 items. In question 1 and 4–8 the satisfaction with the treatment is better if the scores are higher. In questions 2 and 3, lower scores indicate blood glucose levels closer to the ideal, and higher scores indicate problems.

Scores range per item from 6 (very satisfied) to 0 (very dissatisfied); total score range 36 to 0.

T0, T6

Satisfaction and usability of the app

Questionnaire newly developed by the researchers contains questions about the satisfaction with regard to receiving app-triggers, frequency, timing and comprehensibility, see Additional file 1.

All items will be rated on a 5-point Likert scale.

T6^a

Outpatient clinic visits and paramedical health care use

Newly developed questionnaire contains one question on outpatient clinic visits (for patients recruited from primary care) or GP visits (for patients recruited from hospitals) and three questions on paramedical health care use: whether patients have visited a dietician, a physiotherapist or a specialised feet therapist the past 3 months.

All four questions are answered with yes or no. In case of a ‘yes’, patients have to fill in how many times they have visited the physician/therapist.

T3, T6