title: The CLO test in the UK: inappropriate reading and missed results.
abstract: BACKGROUND
  In endoscopy units, the CLO test is frequently used to detect Helicobacter pylori (H. pylori). Informal survey suggested that practice deviated from that recommended, with little account taken of possible confounders such as acid-suppressing medication.
  
  
  OBJECTIVE
  To determine the influence of reading time and acid suppression on CLO tests and to estimate impact on test results in UK endoscopy units.
  
  
  METHODS
  Survey of use of CLO tests. Prospective study of time to positivity and concurrent medication in CLO tests from 782 patients.
  
  
  METHODS
  Forty-eight endoscopy units throughout the UK, and a district hospital endoscopy unit.
  
  
  METHODS
  Eighteen endoscopy units in the old Northern Region, and a random sample of 30 other UK units.
  
  
  METHODS
  Time of reading of CLO tests in UK units, and time to positivity of CLO tests in one hospital.
  
  
  RESULTS
  Endoscopy units most frequently used CLO tests to assess H. pylori colonization, with marked differences in the times when tests were read. Nineteen out of 37 units discarded tests considerably earlier than the recommended 24 h. Over 20% of CLO tests became positive more than 2 h after collection, with 11% taking 24 h to change colour. Acid-suppressing medication prolonged time to positivity.
  
  
  CONCLUSIONS
  The majority of endoscopy units read tests earlier than recommended. Acid-suppressing medication delays the development of CLO tests and may increase numbers of false-negative tests. Endoscopy units should read tests at 24 h and preferably test patients off ulcer healing medication.
authors.affiliation: University of Newcastle Regional School of Medicine, North Tyneside Hospital, North Shields, UK.
authors.forename: M I
authors.initials: MI
authors.lastname: Prince
authors.forename: J S
authors.initials: JS
authors.lastname: Osborne
authors.forename: L
authors.initials: L
authors.lastname: Ingoe
authors.forename: D E
authors.initials: DE
authors.lastname: Jones
authors.forename: I
authors.initials: I
authors.lastname: Cobden
authors.forename: J R
authors.initials: JR
authors.lastname: Barton
mesh_terms: D005069:Evaluation Studies as Topic; D005188:False Negative Reactions; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000378:metabolism; D016480:Helicobacter pylori / Q000201:enzymology* / Q000302:isolation & purification*; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D006801:Humans; D011446:Prospective Studies; D054328:Proton Pump Inhibitors; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012680:Sensitivity and Specificity; D013997:Time Factors; D006113:United Kingdom; D014510:Urease / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D006635:Histamine H2 Antagonists; D054328:Proton Pump Inhibitors; D011933:Reagent Kits, Diagnostic; D014510:Urease