title: Measuring irritable bowel syndrome patient-reported outcomes with an abdominal pain numeric rating scale.
abstract: BACKGROUND
  Controversy exists on how to measure patient-reported outcomes in irritable bowel syndrome (IBS) clinical trials effectively. Pain numeric rating scales (NRS) are widely used in the non-IBS pain literature. The Food and Drug Administration has proposed using the NRS in IBS.
  
  
  OBJECTIVE
  To test the psychometrics of an abdominal pain NRS in IBS. Methods We analysed data from a longitudinal cohort of Rome III IBS subjects. At entry, subjects completed a 10-point NRS, bowel symptoms, IBS severity measurements (IBS-SSS, FBDSI), health-related quality of life indices (IBS-QOL, EQ5D), and the Worker Productivity Activity Index (WPAI). We repeated assessments at 3 months along with a response scale to calculate the minimal clinically important difference.
  
  
  RESULTS
  There were 277 subjects (82% women; age = 42 +/- 15) at baseline and 90 at 3 months. The NRS correlated cross-sectionally with IBS-SSS (r = 0.60; P < 0.0011), FBDSI (r = 0.49; P < 0.0001), IBS-QOL (r = 0.43; P < 0.0001), EQ5D (r = 0.48; P < 0.0001), presenteeism (r = 0.39; P < 0.0001), absenteeism (r = 0.17; P = 0.04) and distension (r = 0.46; P < 0.0001), but not stool frequency or form. The minimal clinically important difference was 2.2 points, correlating with a 29.5% reduction over time.
  
  
  CONCLUSIONS
  An abdominal pain NRS exhibits excellent validity and can be readily interpreted with a minimal clinically important difference in patients with IBS. These data support the use of the NRS in IBS clinical trials.
authors.affiliation: VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA. bspiegel@mednet.ucla.edu
authors.forename: B
authors.initials: B
authors.lastname: Spiegel
authors.forename: R
authors.initials: R
authors.lastname: Bolus
authors.forename: L A
authors.initials: LA
authors.lastname: Harris
authors.forename: S
authors.initials: S
authors.lastname: Lucak
authors.forename: B
authors.initials: B
authors.lastname: Naliboff
authors.forename: E
authors.initials: E
authors.lastname: Esrailian
authors.forename: W D
authors.initials: WD
authors.lastname: Chey
authors.forename: A
authors.initials: A
authors.lastname: Lembo
authors.forename: H
authors.initials: H
authors.lastname: Karsan
authors.forename: K
authors.initials: K
authors.lastname: Tillisch
authors.forename: J
authors.initials: J
authors.lastname: Talley
authors.forename: E
authors.initials: E
authors.lastname: Mayer
authors.forename: L
authors.initials: L
authors.lastname: Chang
mesh_terms: D015746:Abdominal Pain / Q000523:psychology*; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016896:Treatment Outcome