title: Factor analysis of bowel symptoms in US and Italian populations.
abstract: OBJECTIVE
  Functional gastrointestinal disorders are diagnosed by the presence of a characteristic set of symptoms. Aims of this study were to validate the Rome symptom criteria by factor analysis and to determine whether symptoms cluster in the same way in different cultures.
  
  
  METHODS
  One thousand forty-one gastroenterology clinic patients in the US (response rate 53%) and 228 family members accompanying clinic patients in Italy (84%) completed a previously validated symptom questionnaire. Factor analysis identified clusters of symptoms which are highly correlated with each other, and these were compared to the Rome diagnostic criteria.
  
  
  RESULTS
  In the US, 13 factors were identified. The irritable bowel factor was composed of three core symptoms corresponding to the Rome II classification system. Two dyspepsia factors were identified which correspond to the ulcer- and motility-like subtypes proposed in the Rome I classification system. All symptoms of constipation formed a single cluster as proposed in the Rome II classification system. Symptom clusters in the US agreed well with symptom clusters identified in Italian subjects.
  
  
  CONCLUSIONS
  Empirically derived symptom clusters agree in most respects with the Rome II classification system and support their validity. These symptom clusters are independent of cultural differences in diet and behaviour.
authors.affiliation: UNC Center for Functional Gastrointestinal and Motility Disorders, University of North Carolina at Chapel Hill, Chapel Hill, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Whitehead
authors.forename: G
authors.initials: G
authors.lastname: Bassotti
authors.forename: O
authors.initials: O
authors.lastname: Palsson
authors.forename: E
authors.initials: E
authors.lastname: Taub
authors.forename: E C
authors.initials: EC
authors.lastname: Cook
authors.forename: D A
authors.initials: DA
authors.lastname: Drossman
mesh_terms: D000328:Adult; D000334:Aerophagy / Q000150:complications; D000554:Ambulatory Care Facilities; D003109:Colonic Diseases, Functional / Q000175:diagnosis* / Q000208:ethnology; D003248:Constipation / Q000150:complications; D003967:Diarrhea / Q000150:complications; D004415:Dyspepsia / Q000150:complications; D004935:Esophageal Diseases / Q000150:complications; D005163:Factor Analysis, Statistical; D005260:Female; D005764:Gastroesophageal Reflux / Q000150:complications; D006356:Heartburn / Q000150:complications; D006801:Humans; D007558:Italy; D008297:Male; D010146:Pain / Q000150:complications / Q000503:physiopathology; D011795:Surveys and Questionnaires; D014481:United States