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

Background : There is an ongoing debate about the optimal test drink to be used in the 13 C‐urea breath test ( 13 C‐UBT). We recently reported that a citric acid solution is the optimal test drink in the 13 C‐UBT, because it provides a high 13 CO 2 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 13 C‐UBT. Aim : To compare the diagnostic accuracy of the 13 C‐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 13 C‐UBT was performed on two consecutive days by giving 75 mg of 13 C‐urea randomly dissolved in 200 mL 0.1 M citric acid solution or 200 mL orange juice. The 13 CO 2 / 12 CO 2 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 13 C‐sodium acetate breath test; 50 mg of 13 C‐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‰ vs. 23.2 ± 3.4‰, 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 13 C‐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 : 13 C‐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 13 C‐UBT.