title: The effect of dosing with omeprazole on the accuracy of the 13C-urea breath test in Helicobacter pylori-infected subjects.
abstract: BACKGROUND
  The 13C-urea breath test (13C-UBT) is an accurate means of Helicobacter pylori diagnosis. However, proton pump inhibitors may suppress H. pylori and cause false negative results.
  
  
  OBJECTIVE
  To study the kinetics of H. pylori suppression by omeprazole during and after short-term use.
  
  
  METHODS
  Volunteers underwent a baseline 13C-UBT (13C-urea 100 mg). H. pylori-positive subjects took omeprazole 20 mg daily for 14 days. Those who remained 13C-UBT positive (delta13CO2 >/= 5) continued omeprazole for a further 14 days. 13C-UBTs were performed weekly on omeprazole and then every second day after it was stopped. False negatives occurred when delta13CO2 fell to < 5.
  
  
  RESULTS
  In 25 H. pylori-positive subjects (mean age 43.9 +/- 2.4 years; 21 females, 4 males) the mean baseline delta13CO2 was 28.1 +/- 3.4. False negative breath tests occurred in three subjects after 7 days of omeprazole and in a further four subjects after 14 days. A further six subjects developed negative tests between Days 14 and 28. Following cessation of omeprazole, the 13C-UBT became positive again in 12/13 subjects within 4 days and in all within 6 days, with a mean recovery to 99.9 +/- 18.6% of baseline delta13CO2.
  
  
  CONCLUSIONS
  False negative 13C-UBTs are common during treatment with omeprazole and occur after as little as 7 days. Return to positive test results is rapid after cessation of omeprazole. These findings are relevant to the timing of testing in clinical practice.
authors.affiliation: Gastroenterology Unit, The University of Sydney, Concord Hospital, Sydney, Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Connor
authors.forename: F
authors.initials: F
authors.lastname: Seow
authors.forename: M C
authors.initials: MC
authors.lastname: Ngu
authors.forename: P H
authors.initials: PH
authors.lastname: Katelaris
mesh_terms: D000328:Adult; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D001944:Breath Tests / Q000379:methods; D002250:Carbon Radioisotopes; D005188:False Negative Reactions; D005260:Female; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000188:drug therapy; D016480:Helicobacter pylori / Q000187:drug effects; D006801:Humans; D008297:Male; D009853:Omeprazole / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014508:Urea
chemical_list: D000897:Anti-Ulcer Agents; D002250:Carbon Radioisotopes; D014508:Urea; D009853:Omeprazole