title: Impact of different pH thresholds for 24-hour dual probe pH monitoring in patients with suspected laryngopharyngeal reflux.
abstract: OBJECTIVE
  The gold standard test for laryngopharyngeal reflux is 24-hour pH monitoring, which determines the reflux area index with a pH threshold of less than four (i.e. the reflux area index four). However, refluxed pepsin is able to cause laryngeal injury at pH levels above five.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  In order to establish normative values for a reflux area index with a pH threshold of less than five (i.e. the reflux area index five), 29 healthy volunteers underwent pH monitoring. In 45 patients with suspected laryngopharyngeal reflux, reflux area index four and reflux area index five were determined by pH study.
  
  
  RESULTS
  In healthy volunteers, the reflux area index five was 72.6 (95th percentile). In 29 of 44 patients, laryngopharyngeal reflux was diagnosed due to a reflux area index four of greater than 6.3. However, the reflux area index five revealed laryngopharyngeal reflux in six more patients.
  
  
  CONCLUSIONS
  For exact analysis of pH monitoring results, two pH thresholds (less than four and less than five) must be considered. Further studies with a larger number of healthy volunteers are necessary in order to reveal normative values for the reflux area index five parameter.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig Maximilians University Munich, Germany. entdoc@gmx.net
authors.forename: O
authors.initials: O
authors.lastname: Reichel
authors.forename: W J
authors.initials: WJ
authors.lastname: Issing
mesh_terms: D050782:Esophageal pH Monitoring; D005260:Female; D005745:Gastric Acidity Determination; D005764:Gastroesophageal Reflux / Q000175:diagnosis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007818:Laryngeal Diseases / Q000175:diagnosis*; D007830:Larynx / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010434:Pepsin A / Q000378:metabolism; D010608:Pharyngeal Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D012016:Reference Values
chemical_list: D010434:Pepsin A