title: Psychometric evaluation of patient-reported outcomes in irritable bowel syndrome randomized controlled trials: a Rome Foundation report.
abstract: OBJECTIVE
  There is debate about how best to measure patient-reported outcomes (PROs) in irritable bowel syndrome (IBS). We pooled data to measure the psychometric properties of IBS end points, including binary responses (eg, "adequate relief") and 50% improvement in symptom severity.
  
  
  METHODS
  We pooled data from 12 IBS drug trials involving 10,066 participants. We tested the properties of binary response and 50% improvement end points, including the impact of baseline severity on performance, and measured construct validity using clinical anchors.
  
  
  RESULTS
  There were 9044 evaluable subjects (age, 44 years; 85% female; 58% IBS constipation-prominent [IBS-C]; 31% IBS diarrhea-prominent [IBS-D]). Using the binary end point, the proportion responding in the mild, moderate, and severe groups was 42%, 40%, and 38%, respectively (P = .0008). There was no effect of baseline severity on binary response (odds ratio [OR], 0.99; 95% confidence interval [CI], 0.99-1.0; P = .07). The proportions reaching 50% improvement in pain were 45%, 41%, and 41%, respectively; there was a small, yet significant, impact of baseline severity (OR, 1.04; 95% CI, 1.03-1.05; P < .0001) that did not meet clinical relevance criteria. Both end points revealed strong construct validity and detected "minimally clinically important differences" in symptoms. Both provided better discriminant spread in IBS-D than IBS-C.
  
  
  CONCLUSIONS
  Both the traditional binary and 50% improvement end points are equivalent in their psychometric properties. Neither is impacted by baseline severity, and both demonstrate excellent construct validity. They are optimized for the IBS-D population but also appear valid in IBS-C.
authors.affiliation: Department of Medicine, VA Greater Los Angeles Healthcare System, Los Angeles, California, USA. bspiegel@mednet.ulca.edu
authors.forename: Brennan
authors.initials: B
authors.lastname: Spiegel
authors.forename: Michael
authors.initials: M
authors.lastname: Camilleri
authors.forename: Roger
authors.initials: R
authors.lastname: Bolus
authors.forename: Viola
authors.initials: V
authors.lastname: Andresen
authors.forename: William D
authors.initials: WD
authors.lastname: Chey
authors.forename: Sheri
authors.initials: S
authors.lastname: Fehnel
authors.forename: Allen
authors.initials: A
authors.lastname: Mangel
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Talley
authors.forename: William E
authors.initials: WE
authors.lastname: Whitehead
mesh_terms: D015746:Abdominal Pain / Q000209:etiology / Q000517:prevention & control* / Q000523:psychology; D000328:Adult; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D010147:Pain Measurement; D017060:Patient Satisfaction; D011237:Predictive Value of Tests; D011594:Psychometrics; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016896:Treatment Outcome
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