title: Citric acid or orange juice for the 13C-urea breath test: the impact of pH and gastric emptying.
abstract: BACKGROUND
  There is an ongoing debate about the optimal test drink to be used in the 13C-urea breath test (13C-UBT). We recently reported that a citric acid solution is the optimal test drink in the 13C-UBT, because it provides a high 13CO2 recovery and the excellent accuracy of the test appears optimal compared to other test meals. Orange juice, because of a better taste, is also propagated as a test drink in the 13C-UBT.
  
  
  OBJECTIVE
  To compare the diagnostic accuracy of the 13C-UBT with either orange juice or citric acid solution as a test drink. Furthermore, the effect of these test drinks on the gastric emptying rate was determined.
  
  
  METHODS
  H. pylori status was assessed by histology, rapid urease test and culture in 50 consecutive dyspeptic patients. A 13C-UBT was performed on two consecutive days by giving 75 mg of 13C-urea randomly dissolved in 200 mL 0.1 M citric acid solution or 200 mL orange juice. The 13CO2/12CO2 ratio was measured in breath samples taken before and 15, 30, 45 and 60 min after administration of the test drink. The gastric emptying rate of orange juice and citric acid solution was compared to that of water in 10 healthy subjects on three consecutive days by means of a 13C-sodium acetate breath test; 50 mg of 13C-sodium acetate was dissolved in 200 mL of each solution and breath samples were collected before and every 10 min for 90 min after administration of the test drink.
  
  
  RESULTS
  Twenty-six out of 50 patients (52%) were infected with H. pylori. Significantly higher values over baseline (35.7+/-5.2 per thousand vs. 23.2+/-3.4 per thousand, P<0.001) and higher area under the curve (1507+/-198 vs. 927+/-128, P<0.001) were observed in H. pylori-positive patients when citric acid solution was administered compared with orange juice. Sensitivity of the 13C-UBT was 100% when citric acid was used as a test drink and 88% with orange juice. Specificity was 100% with both test drinks. Gastric emptying of citric acid solution (t1/2 = 60.9+/-3.5 min) was significantly slower than that of orange juice (t1/2 = 49.7+/-3.1 min, P<0.001).
  
  
  CONCLUSIONS
  13C-UBT loses diagnostic accuracy when orange juice instead of citric acid is used as a test drink. The faster gastric emptying of orange juice might be responsible for the lower diagnostic accuracy of the 13C-UBT.
authors.affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, University of Magdeburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Leodolter
authors.forename: J E
authors.initials: JE
authors.lastname: Domínguez-Muñoz
authors.forename: U
authors.initials: U
authors.lastname: Von Arnim
authors.forename: P
authors.initials: P
authors.lastname: Malfertheiner
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001628:Beverages; D001944:Breath Tests / Q000379:methods*; D019343:Citric Acid; D002957:Citrus; D005260:Female; D005745:Gastric Acidity Determination; D005746:Gastric Emptying / Q000187:drug effects; D006207:Half-Life; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D014508:Urea
chemical_list: D019343:Citric Acid; D014508:Urea