Citric acid or orange juice for the C-13-urea breath test: the impact of pH and gastric emptying

Background: There is an ongoing debate about the optimal test drink to be u sed in the C-13-urea breath test (C-13-UBT). We recently reported that a ci tric acid solution is the optimal test drink in the C-13-UBT, because it pr ovides a high (CO2)-C-13 recovery and the excellent accuracy of the test ap pears optimal compared to other test meals, Orange juice, because of a bett er taste, is also propagated as a test drink in the C-13-UBT. Aim: To compare the diagnostic accuracy of the C-13- 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 C-13-UBT was performed on t wo consecutive days by giving 75 mg of C-13-urea randomly dissolved in 200 mt 0.1 M citric acid solution or 200 mt orange juice. The (CO2)-C-13/(CO2)- C-12 ratio was measured in breath samples taken before and 15, 30, 45 and 6 0 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 h ealthy subjects on three consecutive days by means of a C-13- sodium acetat e breath test; 50 mg of C-13-sodium acetate was dissolved in 200 mt 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 parts per thousand, vs. 23.2 +/- 3.4 parts per thousand,, P<0.001) and higher area under the c urve (1507 +/- 198 vs. 927 +/- 128, P < 0.001) were observed in H, pylori-p ositive patients when citric acid solution was administered compared with o range juice. Sensitivity of the C-13-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 (t(1/2) = 60.9 +/- 3. 5 min) was significantly slower than that of orange juice (t(1/2) = 49.7 +/ - 3.1 min, P < 0.001). Conclusion: C-13-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 C-17-U BT.