Table 1 Participant timeline in QFS-study

0

Screening

Evaluation of participant’s eligibility for the QFS-study by social pediatrician (and pediatric immunologist/rheumatologist in case of JIA diagnosis).

1

Study visit T0

Participant completes baseline KLIK questionnaires and installs the PROfeel app on smartphone to start ESM measurement. Participant also starts weekly measurement (of fatigue, quality of life, and self-efficacy) on smartphone which lasts throughout the study.

1-4

ESM phase I

Participant starts 4 weeks of ESM, with 5 surveys to answer per day. Surveys contain items inquiring after, e.g., fatigue and other symptoms, (social) activities, and affect in the last 3 h.

5

Study visit T1

Participant completes T1 KLIK questionnaires and is randomly allocated to either 12 weeks of patient-tailored PROfeel lifestyle advice or generic dietary advice. Biological samples (i.e., blood, stool, saliva, and hair) are collected for the first time.

5-16

Intervention I

Participant adheres to allocated advice for 12 weeks. To improve adherence, participant receives a boost from the investigator by phone and/or mail.

17

Study visit T2

Participant completes T2 KLIK questionnaires and evaluates first intervention with investigator. Biological samples (i.e., blood, stool, saliva, and hair) are collected for the second time.

17-20

ESM phase II

Participant starts a second period of 4 ESM weeks, with 5 surveys to answer per day. Survey items are identical to ESM phase I.

21

Study visit T3

Participant completes T3 KLIK questionnaires and is allocated to the other intervention arm (either 12 weeks of patient-tailored PROfeel lifestyle advice or generic dietary advice).

21-32

Intervention II

Participant adheres to allocated advice for 12 weeks. To improve adherence, participant receives a boost from the investigator by phone and/or mail.

33

Study visit T4

Participant completes T4 KLIK questionnaires and evaluates second intervention with investigator. If fatigue remains severe, participant can be referred to ECCF for post-trial care. Biological samples (i.e., blood, stool, saliva, and hair) are collected for the third time.

33-60

Follow-up

Weekly measurement (of fatigue, quality of life, and self-efficacy) on smartphone continues until 12 weeks after T4. During week 60, participant completes follow-up KLIK questionnaires, marking the end of QFS-study participation.