title: Patient-reported outcomes for irritable bowel syndrome are associated with patients' severity ratings of gastrointestinal symptoms and psychological factors.
abstract: OBJECTIVE
  Patient-reported outcomes (PROs) are used to gauge the benefit of treatments for functional gastrointestinal disorders, including irritable bowel syndrome (IBS). Commonly used end points derived from scales of symptom severity differ in their structure, format, and the extent to which they are based on established psychometric fundamentals. We evaluated the overlap between 2 measures of IBS symptom severity, documented their association with different symptoms (pain, bloating, altered defecation), and identified psychological factors that might bias PRO ratings, by affecting how patients interpret IBS symptom severity.
  
  
  METHODS
  Ninety-eight patients diagnosed with IBS, based on Rome III criteria, completed the multicomponent IBS Symptom Severity Scale and the single-item, UCLA Symptom Severity Scale. Data were collected on pain, bloating, and bowel habits, as well as somatization, sensitivity to arousal symptoms (anxiety sensitivity), and a negative thinking style called pain catastrophizing.
  
  
  RESULTS
  The 2 global scales were correlated with one another (r = 0.56); each scale was associated most strongly with variation in abdominal pain. Data were consistent with a model in which pain catastrophizing and somatization influenced 1 or more of patients' judgments of pain, bloating, and/or bowel habits, which then affected the PROs.
  
  
  CONCLUSIONS
  Depending on their structure and format, PROs can have different levels of sensitivity to core IBS symptoms and be influenced by psychological and somatic complaints that are beyond the aim of therapy and labeling claim. PROs that rely on patients' perspectives to index symptom severity can be improved by consideration of psychometric principles that influence self-report.
authors.affiliation: Division of Gastroenterology, Department of Medicine, University at Buffalo School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14215, USA. lackner@buffalo.edu
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lackner
authors.forename: James
authors.initials: J
authors.lastname: Jaccard
authors.forename: Charles
authors.initials: C
authors.lastname: Baum
authors.forename: Amanda
authors.initials: A
authors.lastname: Smith
authors.forename: Susan
authors.initials: S
authors.lastname: Krasner
authors.forename: Leonard
authors.initials: L
authors.lastname: Katz
authors.forename: Rebecca
authors.initials: R
authors.lastname: Firth
authors.forename: Tatayna
authors.initials: T
authors.lastname: Raby
authors.forename: Cathrine
authors.initials: C
authors.lastname: Powell
mesh_terms: D000328:Adult; D016903:Drug Monitoring / Q000379:methods* / Q000523:psychology*; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis / Q000523:psychology* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life / Q000523:psychology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome