title: 13C-urea breath test for the diagnosis of Helicobacter pylori infection before treatment: is citric acid necessary?
abstract: OBJECTIVE
  13C-urea breath test is one of the best methods for the diagnosis of Helicobacter pylori infection. Although a citric acid solution is generally used prior to urea intake, the superiority of this strategy has not been sufficiently demonstrated. Thus, our aim was to compare 13C-urea breath test with and without citric acid solution, to evaluate whether 13C-urea breath test can also achieve favourable results when the test meal is omitted.
  
  
  METHODS
  13C-urea breath test with and without citric acid were compared prospectively in 53 subjects without prior Helicobacter pylori eradication therapy prescription. Basal samples and at 15', 30', and 45' after taking 100 mg of 13C-urea were obtained. The gold standard for Helicobacter pylori diagnosis was the 13C-urea breath test result with citric acid at 30', and "Delta Over Baseline" values >5 at that time were considered positive.
  
  
  RESULTS
  The prevalence of Helicobacter pylori infection was 68%. Mean Delta Over Baseline values with citric acid at 15', 30' and 45' were: 29.6+/-39, 30.8+/-37 and 24.6+/-27; whereas respective values without citric acid were lower: 14.9+/-22, 12.2+/-17 and 10D+/-13 (p<O. 001 for all comparisons, Wilcoxon test for paired data). Thus, the area under the curve (constructed with Delta Over Baseline values at different times) with citric acid was 85+/- 102, and 37+/-50 without citric acid [p<0.001). Correlation coefficient between Delta Over Baseline values with and without citric acid at 30' was 0.73 (p<0.0001). The percentage of subjects achieving the highest Delta Over Baseline value at 15', 30' and 45' with citric acid was 51%, 30% and 19%, whereas without citric acid it was 51%, 26% and 23% (non-significant differences). The area under receiver operating characteristic curve for 13C-urea breath test without citric acid was: 0.98 at 15', 1 at 30' and 0.97 at 45'. The best cut-off point for 13C-urea breath test without citric acid at 30' was anywhere between 3. 3 and 3.9 (that is, a lower value than that usually considered with citric acid), with 100% (95% confidence interval, 90-100%) sensitivity and 100% [82-100%) specificity
  
  
  CONCLUSIONS
  13C-urea breath test values with citric acid are higher than those obtained without citric acid, although this difference does not imply a diagnostic superiority in untreated patients when considering 13C-urea breath test without citric acid at 30'. Therefore, for the diagnosis of Helicobacter pylori infection in untreated patients, citric acid solution in 13C-urea breath test protocol can be omitted.
authors.affiliation: Department of Gastroenterology, University Hospital of La Princesa, Madrid, Spain. gisbert@meditex.es
authors.forename: J P
authors.initials: JP
authors.lastname: Gisbert
authors.forename: M A
authors.initials: MA
authors.lastname: Vazquez
authors.forename: I
authors.initials: I
authors.lastname: Jimenez
authors.forename: A I
authors.initials: AI
authors.lastname: Cruzado
authors.forename: D
authors.initials: D
authors.lastname: Carpio
authors.forename: E
authors.initials: E
authors.lastname: Del Castillo
authors.forename: M J
authors.initials: MJ
authors.lastname: Martin
authors.forename: A
authors.initials: A
authors.lastname: Morales
authors.forename: R
authors.initials: R
authors.lastname: Pajares
authors.forename: A
authors.initials: A
authors.lastname: Rodriguez
authors.forename: J M
authors.initials: JM
authors.lastname: Pajares
mesh_terms: D000328:Adult; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D001706:Biopsy; D001944:Breath Tests; D002250:Carbon Radioisotopes; D002614:Chelating Agents; D019343:Citric Acid; D003937:Diagnosis, Differential; D005260:Female; D005773:Gastroscopy; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D011446:Prospective Studies; D015203:Reproducibility of Results; D013272:Stomach Diseases / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D014508:Urea / Q000032:analysis*
chemical_list: D000890:Anti-Infective Agents; D002250:Carbon Radioisotopes; D002614:Chelating Agents; D019343:Citric Acid; D014508:Urea