title: Slimline vs. glass pH electrodes: what degree of accuracy should we expect?
abstract: BACKGROUND
  Ambulatory pH monitoring is considered the gold standard for measuring oesophageal acid exposure, however, data comparing antimony and glass electrodes are limited.
  
  
  OBJECTIVE
  To compare the accuracy of the Slimline antimony pH monitoring system and a conventional glass electrode catheter pH monitoring system during ambulatory conditions.
  
  
  METHODS
  Eighteen subjects (13 males, 23-45 years) underwent simultaneous pH monitoring using the Slimline antimony pH electrode and MIC M3 glass pH electrode pH monitoring systems for 12 h. Acid exposure was analysed and compared by manual extraction of the data onto an excel spreadsheet.
  
  
  RESULTS
  There was no statistical difference in the median per cent time the pH was <4 recorded by the two systems (Slimline, 3%, Glass MIC M3, 2%, P = 0.77) and the correlation was excellent (r = 0.84). The difference in recorded reflux events was also not significantly different between the two systems, with the absolute difference being 23 events (s.d., 26). Point-by-point discrepancy was 28% (s.d., 18%), however, the agreement in terms of reflex events was excellent (Kappa value, 0.89, s.d., 0.09).
  
  
  CONCLUSIONS
  Despite substantial point-by-point disagreement, the antimony Slimline pH catheter compares favourably to the Glass MIC M3 pH catheter in terms of measuring standard pH parameters.
authors.affiliation: Department of Medicine, Northwestern University, The Feinberg School of Medicine, Chicago, IL 60611, USA. j-pandolfino@northwestern.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Pandolfino
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: Q
authors.initials: Q
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Heath
authors.forename: T
authors.initials: T
authors.lastname: Bombeck
authors.forename: P J
authors.initials: PJ
authors.lastname: Kahrilas
mesh_terms: D000328:Adult; D000965:Antimony; D001628:Beverages / Q000009:adverse effects; D002957:Citrus / Q000009:adverse effects; D004867:Equipment Design; D004947:Esophagus / Q000378:metabolism*; D005260:Female; D005745:Gastric Acidity Determination; D005764:Gastroesophageal Reflux / Q000378:metabolism; D005898:Glass; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods; D012016:Reference Values
chemical_list: D000965:Antimony