Outcome parameters | |
 Behaviour change (stage of change) | Questionnaire containing 1 question per advice received to determine the current stage of change (transtheoretical model (Fig. 4) [43,44,45]). |
 Behaviour change (verification) | Physical activity: the validated Dutch version of the International Physical Activity Questionnaire (IPAQ) [46]. Smoking: questions on current smoking behaviour and quantity of smoking. Dietary and alcohol intake: questions on regular intake of all food groups and alcoholic consumptions, for which advice is received by the participant. Body weight and waist circumference: measured at home by the participant, following detailed instructions and using the same weighing scale each time. |
 Motivational regulation | Validated Treatment Self-Regulation Questionnaire (TSRQ) [47], translated into Dutch. This questionnaire has been modified to ask motivational regulation with regard to the ‘advice given’ and ‘healthy lifestyle’. |
 Attitude | Questionnaire consisting of 7 Likert scale items on outcome expectations, 16 Likert scale items on the reasons for (not) undergoing testing by Health Potential®, 50 Likert scale items on the attitude towards five primary lifestyle behaviours, 1 Likert scale item on the importance of preventing disease, and 6 items on the evaluation of the Health Potential® report. |
 Behaviour-specific self-efficacy | Questionnaire which was developed using the ‘Guide for constructing self-efficacy scales’ by Bandura [48]. It includes one self-efficacy question for each advice given in which the participant indicates on a scale of 0–100% how sure they are of their ability to follow the advice. |
 Risk perception | Likert scale questions on the perceived probability of getting and severity [37] of each of the diseases included in the standard Health Potential® service. |
 Perceived stress | Dutch translation of the validated 14-item Perceived Stress Scale (PSS) [49]. |
 Discussion of test results with health professionals and/or family and friends | Multiple-answer question in which the participant can indicate with whom the results were discussed. |
 Test-related distress (arms 1 and 2 only) | Dutch translation [50, 51] of the validated Impact of Event Scale (IES), which has been used previously to study test-related distress after genetic testing for common disease risk [39]. |
Other study parameters | |
 Self-reported health status | Dutch translation of the validated RAND 36-Item Short Form Health Survey, V2 (SF-36 V2) [52, 53]. |
 Health locus of control | Dutch translation of the validated Multidimensional Health Locus of Control (MHLC) Scale [54, 55]. |
 Comprehension of risk estimates (arms 1 and 2 only) | Questions based on the questions used by Kaufman et al. [56]. |
 Genetic knowledge (arms 1 and 2 only) | Dutch translation of the questions as used by Carere et al. [57]. |
 Cue to action | Two Likert scale questions on whether the participant felt the Health Potential® report and the general health check were a cue to action. |
 Personal and family history of tested diseases | Questionnaire asking about personal and family history. |
 General self-efficacy | Validated Dutch General Self-Efficacy Scale (DGSES) [58]. |
 Social modelling, social support | One Likert scale question per advice received. |
 Social support | One Likert scale question per lifestyle domain (diet, alcohol, physical activity, smoking, body weight). |
 Pro-active coping skills | Validated Utrechtse Pro-actieve Coping Competenties (UPCC) questionnaire [59]. |
 Vitality | Validated Vita-16 [60]. |
 Previous participation in genetic testing | Two yes/no questions. |
 Temporal discounting | Validated 10-item Delaying Gratification Inventory short form, translated into Dutch (DGI-10) [61]. |
 Personality | Validated Dutch IPIP-50 [62]. |