The
urea breath test (UBT) is often used to diagnose Helicobacter pylori
infection and for its eradication. However, this text can give positive results even for other
urease-active bacteria other than H. pylori. Even after the successful eradication of H. pylori, the presence of other
urease-active bacteria in the gut and oral cavity can lead to positive UBT results in patients with decreased gastric acid secretion. Herein, a 15-year-old boy was diagnosed with H. pylori
infection through the testing and treatment program for H. pylori for third-year junior high-school students in Saga Prefecture initiated in 2016. He underwent triple
therapy comprising
vonoprazan; however, UBT was found to be positive even after
therapy. The results remained positive even after fourth-line eradication
therapy. Stool
antigen, PCR using gastric fluid, microscopy, culture, and rapid
urease tests were all negative.
Pepsinogen levels were normal, and none of the findings suggested autoimmune
gastritis. Gastric microflora analysis revealed oral flora showing
urease activity. UBT is considered useful for determining the successful eradication of H. pylori; however, it may give false-positive results for both H. pylori
infection and eradication judgment. Although the patient did not have autoimmune
gastritis or decreased gastric acid secretion, it is presumed that oral commensal bacteria showing
urease activity inhabited the stomach, resulting in the persistently positive UBT results. In conclusion, repeated false-positive UBT results for H. pylori may occur even without gastric acid hyposecretion. If H. pylori eradication is unsuccessful based on UBT, additional test by stool H. pylori
antigen tests should be considered.