title: Normal limits of 14C-urea breath test.
abstract: OBJECTIVE
  14C-urea breath test has been widely used for diagnosis of Helicobacter pylori (H. pylori) infection. There is no general agreement on the cutoff values for determination of H. pylori negative subjects. We studied baseline values in subjects who were proved to be H. pylori negative and calculated the cutoff value of normalcy. A comparison of this test with other tests for diagnosis of H. pylori infection was also done.
  
  
  METHODS
  12 patients (mean age 34 +/- 14, range 22-65 years; 8 men) of non-ulcer dyspepsia were studied, who were proved to be H. pylori negative by rapid urease test, Gram's staining, histopathology and culture of gastric mucosal biopsies obtained four each from the antrum, body and fundus of the stomach. The controls included 12 patients (mean age 40 +/- 13, range 22-65 years, 9 men), who were positive for H. pylori on culture or combination of rapid urease test and histopathology or rapid urease test and Gram's stain. 14C-urea breath test was performed using 5 uCi of 14C-urea dissolved in 300 ml of water. Breath samples were collected once before ingestion of 14C urea and subsequently at 5, 15 and 30 minutes after ingestion and 14C-contents in the breath samples measured. Results were expressed as 14 CO2/mmol CO2 exhaled as percent of administered urea.
  
  
  RESULTS
  The mean +/- SD 14-C value in H. pylori negative vs H. pylori positive patients at 5 minutes, 15 minutes and 30 minutes were found to be 0.003 +/- 0.003 vs 0.064 +/- 0.042 (p < 0.001), 0.002 +/- 0.001 vs 0.056 +/- 0.039 (p < 0.001) and 0.001 +/- 0.002 vs 0.041 +/- 0.026 (p < 0.001) respectively. The mean values of 14C-urea breath test were significantly lower in H. pylori negative patients as compared to H. pylori positive patients. Using receiver operating characteristic (ROC) analysis of the data, the cutoff values obtained were 0.01, 0.007 and 0.009 at 5 minutes, 15 minutes and 30 minutes respectively.
  
  
  CONCLUSIONS
  14C-urea breath test levels at 5, 15 and 30 minutes intervals are significantly lower in H. pylori negative patients as compared to H. pylori positive patients. This test has high sensitivity and specificity in detecting H. pylori infection.
authors.affiliation: Department of Gastroenterology, Postgraduate Institute of Medical Education and Research, Chandigarh.
authors.forename: A
authors.initials: A
authors.lastname: Kaul
authors.forename: D K
authors.initials: DK
authors.lastname: Bhasin
authors.forename: C M
authors.initials: CM
authors.lastname: Pathak
authors.forename: P
authors.initials: P
authors.lastname: Ray
authors.forename: K
authors.initials: K
authors.lastname: Vaiphei
authors.forename: B C
authors.initials: BC
authors.lastname: Sharma
authors.forename: K
authors.initials: K
authors.lastname: Singh
mesh_terms: D000328:Adult; D000368:Aged; D001944:Breath Tests; D002250:Carbon Radioisotopes; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D004415:Dyspepsia / Q000382:microbiology*; D005260:Female; D016481:Helicobacter Infections / Q000175:diagnosis*; D016480:Helicobacter pylori / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014508:Urea / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D014508:Urea