title: Clustering and stability of functional lower gastrointestinal symptom after enteric infection.
abstract: BACKGROUND
  Current diagnostic criteria for functional gut disorder are based on symptom clusters observed after sporadic onset. It remains unclear whether symptoms group similarly in functional disorders of postinfectious etiology. We utilized observational data from the Walkerton Health Study (WHS) to: (i) determine groupings of functional gastrointestinal symptoms among patients exposed to acute gastroenteritis (GE), and (ii) assess the stability of these symptoms grouping over time.
  
  
  METHODS
  WHS participants 16 years of age and older at the time of the outbreak were included, if they had completed a modified Talley's Bowel Disease Questionnaire (BDQ) and responded 'yes' to a screening question as to whether they had experienced abdominal pain in the last 2 weeks. Exploratory factor analysis (EFA) using tetrachoric correlations was undertaken to identify symptom constructs. Hierarchical cluster analysis using the k-means method was used to create cluster groupings of patients based on these factors. Confirmatory factors analysis using responses to BDQ questionnaire administered at 4, 6, and 8 years after the outbreak was performed to assess stability of symptom domains over time.
  
  
  RESULTS
  A total of 773 participants were eligible for inclusion [62.2% female, mean age 43.1 years (SD = 16.9)]. Eighty-four percent were exposed to acute GE during the outbreak. Two symptom groupings of abdominal pain with either diarrhea or constipation together explained 85.7% of the total variance. Cluster analysis identified four patients groupings based on these factors. These clusters could be qualitatively described as diarrhea- and constipation-predominant, mixed bowel pattern, and no predominance of bowel movements abnormalities. Results of the confirmatory factor analysis validating symptom domains identified in Year 1 showed that the baseline model was acceptable at 4 and 6 years after the outbreak and approached acceptability at 8 years. Values of root mean square error of approximation were 0.071 (90% CI: 0.053, 0.089) at 4 and 0.071 (90% CI: 0.049, 0.092) at 6 years and 0.089 (90% CI: 0.065, 0.114) at 8 years.
  
  
  CONCLUSIONS
  The majority of subjects with postinfectious functional bowel disorders belong to groups with symptoms of abdominal pain and either diarrhea or constipation. These symptom groupings were stable across time.
authors.affiliation: Division of Gastroenterology, Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, ON, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Thabane
authors.forename: M
authors.initials: M
authors.lastname: Simunovic
authors.forename: N
authors.initials: N
authors.lastname: Akhtar-Danesh
authors.forename: A X
authors.initials: AX
authors.lastname: Garg
authors.forename: W F
authors.initials: WF
authors.lastname: Clark
authors.forename: J K
authors.initials: JK
authors.lastname: Marshall
mesh_terms: D015746:Abdominal Pain / Q000453:epidemiology*; D000293:Adolescent; D000328:Adult; D016000:Cluster Analysis; D003248:Constipation / Q000453:epidemiology*; D004196:Disease Outbreaks; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology*; D005767:Gastrointestinal Diseases / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011795:Surveys and Questionnaires