title: Prevalence of gastrointestinal symptoms: heterogeneity of questionnaire studies.
authors.forename: Vui Heng
authors.initials: VH
authors.lastname: Chong
mesh_terms: D015340:Epidemiologic Research Design; D005767:Gastrointestinal Diseases / Q000453:epidemiology*; D006801:Humans; D007492:Iran; D015995:Prevalence; D011795:Surveys and Questionnaires