title: Chronic fatigue in patients with unexplained self-reported food hypersensitivity and irritable bowel syndrome: validation of a Norwegian translation of the Fatigue Impact Scale.
abstract: BACKGROUND
  Patients with unexplained self-reported food hypersensitivity and irritable bowel syndrome (IBS) suffer from several health complaints, including fatigue. The aim of the present study was to validate a Norwegian translation of the Fatigue Impact Scale (FIS), and to assess the impact of fatigue in patients with self-reported food hypersensitivity and IBS, as compared with healthy controls.
  
  
  METHODS
  Thirty-eight patients with unexplained self-reported food hypersensitivity and IBS, who participated in the validation of the FIS completed the following additional questionnaires: the Short Form of Nepean Dyspepsia Index for assessment of quality of life, the Subjective Health Complaint Inventory, and questionnaires for diagnosis and severity of IBS. Impact of fatigue was studied in 43 patients with unexplained self-reported food hypersensitivity, 70% diagnosed with IBS, and 42 healthy controls.
  
  
  RESULTS
  Cronbach's α for the FIS was 0.98, indicating excellent agreement between individual items. Scores on the FIS correlated with scores on the Short Form of Nepean Dyspepsia Index (r = 0.50, P = 0.001), indicating good convergent validity, and were higher in patients (median 85.0, interquartile range 36.8-105.3) than in controls (median 14.0, interquartile range 3.0-29.0, P ≤ 0.0001).
  
  
  CONCLUSIONS
  The Norwegian translation of the FIS performed excellently in patients with unexplained self-reported food hypersensitivity and IBS, with patients reporting significantly more impact of chronic fatigue than healthy controls.
authors.affiliation: Department of Medicine, Haukeland University Hospital, Bergen.
authors.forename: Ragna
authors.initials: R
authors.lastname: Lind
authors.forename: Arnold
authors.initials: A
authors.lastname: Berstad
authors.forename: Jan
authors.initials: J
authors.lastname: Hatlebakk
authors.forename: Jørgen
authors.initials: J
authors.lastname: Valeur
keywords: fatigue; food hypersensitivity; irritable bowel syndrome; quality of life