title: Reliability of 24-hour oesophageal pH monitoring under standardized conditions.
abstract: BACKGROUND
  Twenty-four-hour pH monitoring is an investigation technique that can give both false-positive and false-negative results, depending on patient factors such as diet and different activities. The aim was to study the reproducibility of 24-h oesophageal pH monitoring under as standardized conditions as possible in patients with symptoms of gastro-oesophageal reflux disease.
  
  
  METHODS
  Antimony pH electrodes were used in 22 adult patients who were investigated twice, 6 weeks apart, under identical conditions. They were hospitalized and were served a standardized diet which had been tested to contain no lower than pH 5.0. Neither coffee nor smoking was allowed. The patients had to refrain from proton-pump inhibitors for 10 days and H2 blockers for 2 days prior to the investigation. The paired t test was used.
  
  
  RESULTS
  There was no significant difference in total reflux time, upright or supine reflux time, or longest reflux periods between the two test occasions. However, there were discordant results in six patients who had normal total reflux time on one test occasion but pathological results on the other.
  
  
  CONCLUSIONS
  Since the biological variability of gastro-oesophageal reflux is not negligible from time to time, a normal 24-h oesophageal pH test should be assessed with caution.
authors.affiliation: Dept of Medico-Surgical Gastroenterology, University Hospital, Linköping, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Franzén
authors.forename: L Tibbling
authors.initials: LT
authors.lastname: Grahn
mesh_terms: D000328:Adult; D000368:Aged; D004947:Esophagus / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005764:Gastroesophageal Reflux / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011187:Posture / Q000502:physiology; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors