Quantitative result of ¹³C urea breath test at 15 minutes may correlate with the bacterial density of H. pylori in the stomach

BACKGROUND/AIMS: We tried to test the diagnostic efficacy of a new ¹³C-labeled urea agent made in Taiwan for urea breath test (UBT) of H. pylori infection, and to assess the correlation between the bacterial load of H. pylori in the stomach and the results of UBT from different timings. METHODOLOGY: One hundred and ninety-six dyspeptic patients without usage of antibiotics and proton pump inhibitors in the last 4 weeks were recruited for endoscopy, which included CLO test and H. pylori culture. Three additional bits of gastric biopsy (each one from antrum, body, and cardia) were taken for histology to assess the H. pylori density (HPD, range 0-5) in each specimen and the total bacterial density (TBD, a sum of HPD from three sites, range 0-15). Every study patient had been assigned to complete the UBT protocol. The gas samplings of UBT at baseline, 15 min and 30 min after ingestion of 100 mg ¹³C-labeled urea (INER-Hp ¹³C-tester®, Taiwan) were collected for the ratio of ¹³CO₂/¹²CO₂ and labeled A, B, and C respectively. Both Δ15 (B minus A) and Δ30 (C minus A) were recorded to express the excess δ¹³CO₂ per milliliter. During the 30 min period of UBT, the patient was scheduled to change lying positions every 5 minutes for even coating of the stomach with test agent. RESULTS: Based on two positive results of three invasive methods (CLO test, culture, and histology), 91 cases were confirmed to have H. pylori infection. The diagnostic efficacy of UBT was quite good with 96.7% sensitivity for both Δ15 and Δ30, and with 97.1% and 96.2% specificity for Δ15 and Δ30 respectively. Both Δ15 and Δ30 of UBT were well correlated with the TBD of H. pylori in histology (Δ15: r = 0.7574; Δ30: r = 0.7432, p < 0.0001). CONCLUSIONS: The new C's-labeled urea for UBT can achieve a high diagnostic yield for H. pylori infection. Furthermore, the density of H. pylori in the stomach can be assessed indirectly by UBT by applying 15-minute gas sampling.