Flow chart of the DOK study. The PCP or pediatric gastroenterologist selects eligible children. At baseline inclusion, exclusion criteria and red flag symptoms are determined. The parents and child ≥10 years complete two questionnaires, i.e. a Questionnaire on Pediatric Gastrointestinal Symptoms (QPGS) and a symptoms questionnaire, in addition feces (parasites and colon pathogens) are obtained. Children meeting 1 ≥ red flag symptoms are evaluated for eligibility for endoscopy by a pediatric gastroenterologist. Children without red flag symptoms receive a 1-year follow-up. The arrows indicate that the PCP can refer a child during follow-up for endoscopic evaluation and the children who are not eligible for endoscopy receive a follow-up. After 1 year, information about diagnosis and clinical symptoms is collected based on the two above-mentioned questionnaires.