title: Acid-based parameters on pH-impedance testing predict symptom improvement with medical management better than impedance parameters.
abstract: OBJECTIVE
  pH-impedance testing detects reflux events irrespective of pH, but its value in predicting treatment outcome is unclear. We prospectively evaluated subjects treated medically after pH-impedance testing to determine predictors of symptom improvement.
  
  
  METHODS
  Subjects referred for pH-impedance testing completed questionnaires in which dominant symptoms and global symptom severity (GSS) were recorded. Acid-reflux parameters (acid-exposure time, AET; symptom association by Ghillebert probability estimate, GPE; symptom index, SI) and impedance reflux parameters (reflux-exposure time, RET; number of reflux events; GPE and SI with impedance data) were extracted. Symptoms and GSS were prospectively reevaluated after medical therapy. Univariate and multivariate analyses determined predictors of GSS improvement following medical management.
  
  
  RESULTS
  Over 5 years, 128 subjects (mean 53.3±1.3 years, 66.4% female; typical symptoms 57.0%, 53.9% tested on therapy) underwent pH-impedance testing and subsequent medical therapy for reflux symptoms, and completed required questionnaires. On follow-up 3.35±0.14 years later, mean GSS declined by 45.0%, with 42.2% patients reporting ≥50% GSS improvement. On univariate analysis, total AET, AET≥4.0%, and GPE for all reflux events predicted both linear and ≥50% GSS improvement, but RET and number of reflux events did not. On multivariate analysis, controlling for testing on or off therapy, only AET (P=0.003) and GPE for all reflux events (P=0.029) predicted GSS improvement.
  
  
  CONCLUSIONS
  Acid-based reflux parameters offer greater value over impedance-based nonacid-reflux parameters in predicting symptomatic responses to proton pump inhibitor (PPI) therapy. Our findings support conducting pH-impedance studies off PPI therapy to maximize clinical utility in predicting outcome.
authors.affiliation: Division of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Patel
authors.affiliation: Division of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Sayuk
authors.affiliation: Division of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: C Prakash
authors.initials: CP
authors.lastname: Gyawali
mesh_terms: D000328:Adult; D000368:Aged; D017097:Electric Impedance; D050782:Esophageal pH Monitoring; D004947:Esophagus / Q000503:physiopathology*; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
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