title: Systematic review: role of acid, weakly acidic and weakly alkaline reflux in gastro-oesophageal reflux disease.
abstract: BACKGROUND
  The importance of weakly acidic and weakly alkaline reflux in gastro-oesophageal reflux disease (GERD) is gaining recognition.
  
  
  OBJECTIVE
  To quantify the proportions of reflux episodes that are acidic (pH <4), weakly acidic (pH 4-7) and weakly alkaline (pH >7) in adult patients with GERD, and to evaluate their correlation with symptoms.
  
  
  METHODS
  Studies were identified by systematic PubMed and Embase searches. Data are presented as sample-size weighted means and 95% confidence intervals.
  
  
  RESULTS
  In patients with GERD taking a proton pump inhibitor (PPI), 80% (76-84%) of reflux episodes were weakly acidic or weakly alkaline and 83% (78-88%) of reflux symptom episodes were associated with weakly acidic or weakly alkaline reflux episodes. In patients with GERD not taking a PPI, 63% (59-67%) of reflux episodes were acidic and 72% (57-87%) of reflux symptom episodes were associated with acid reflux episodes. Six studies presented data separately for weakly alkaline reflux, which accounted for <5% of all reflux episodes, both on and off PPI therapy.
  
  
  CONCLUSIONS
  Weakly acidic reflux underlies the majority of reflux episodes in patients with GERD on PPI therapy, and is the main cause of reflux symptoms occurring despite PPI therapy.
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, The Netherlands. Guy.Boeckxstaens@med.kuleuven.be
authors.forename: G E
authors.initials: GE
authors.lastname: Boeckxstaens
authors.forename: A
authors.initials: A
authors.lastname: Smout
mesh_terms: D000328:Adult; D005260:Female; D005745:Gastric Acidity Determination; D005764:Gastroesophageal Reflux / Q000175:diagnosis / Q000209:etiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D054328:Proton Pump Inhibitors / Q000627:therapeutic use
chemical_list: D054328:Proton Pump Inhibitors