title: Validating biomarkers of treatable mechanisms in irritable bowel syndrome.
abstract: BACKGROUND
  A valid biomarker is 'an indicator of normal biologic or pathogenic processes, or pharmacological responses to a therapeutic intervention'. There is no validated biomarker for irritable bowel syndrome (IBS). The aim of the study was to assess ability of three quantitative traits to identify treatable processes to discriminate between IBS-diarrhea (IBS-D) patients, IBS-constipation (IBS-C) patients and healthy volunteers (HV).
  
  
  METHODS
  In 30 HV, 30 IBS-C patients and 64 IBS-D patients, we characterized bowel symptoms and quantitated pathophysiological mechanisms: bile acid (BA) synthesis (serum C4 and FGF19), fecal BA and fat, colonic transit (CT), and intestinal permeability (IP). We used multiple logistic regression and receiver-operating characteristic (ROCAUC ) to appraise three factors (fecal BA, CT, and IP) individually and in combination to identify discriminant targets for treatment in IBS.
  
  
  RESULTS
  There were significant associations between the three subgroups and symptoms reflecting bowel function and the quantitative traits. There were significant associations between fecal BA and CT at 48 h (r = 0.43; p < 0.001) and between fecal BA and IP (r = 0.23; p = 0.015). Individually, fecal BA and CT48 (but not IP) were significant independent predictors for distinguishing HV from IBS. In combination, they discriminated HV from IBS-D patients (ROCAUC 0.70), HV from IBS-C patients (ROCAUC 0.73), and IBS-C patients from IBS-D patients (ROCAUC 0.86). Colonic transit and fecal BA excretion together discriminate between healthy volunteers and IBS-C patients or IBS-D patients, or between the IBS subgroups with 75-90% specificity at 60% sensitivity.
  
  
  CONCLUSIONS
  Colonic transit and fecal BA individually and together constitute useful biomarkers to identify treatable mechanisms in IBS and to differentiate subgroups of IBS.
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (C.E.N.T.E.R.), Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: M
authors.initials: M
authors.lastname: Camilleri
authors.forename: A
authors.initials: A
authors.lastname: Shin
authors.forename: I
authors.initials: I
authors.lastname: Busciglio
authors.forename: P
authors.initials: P
authors.lastname: Carlson
authors.forename: A
authors.initials: A
authors.lastname: Acosta
authors.forename: A E
authors.initials: AE
authors.lastname: Bharucha
authors.forename: D
authors.initials: D
authors.lastname: Burton
authors.forename: J
authors.initials: J
authors.lastname: Lamsam
authors.forename: A
authors.initials: A
authors.lastname: Lueke
authors.forename: L J
authors.initials: LJ
authors.lastname: Donato
authors.forename: A R
authors.initials: AR
authors.lastname: Zinsmeister
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001647:Bile Acids and Salts / Q000032:analysis* / Q000096:biosynthesis; D015415:Biomarkers / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003181:Complement C4 / Q000032:analysis; D003248:Constipation / Q000209:etiology; D003967:Diarrhea / Q000209:etiology; D005243:Feces / Q000737:chemistry; D005260:Female; D005346:Fibroblast Growth Factors / Q000097:blood; D005772:Gastrointestinal Transit / Q000502:physiology; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010539:Permeability; D012372:ROC Curve; D012680:Sensitivity and Specificity
chemical_list: D001647:Bile Acids and Salts; D015415:Biomarkers; D003181:Complement C4; C117476:FGF19 protein, human; D005346:Fibroblast Growth Factors
keywords: bile acid; colon; permeability; transit