[Infection status of Helicobacter pylori with antibody values of 3.0U/mL or more and less than 10.0U/mL in the LZ test "Eiken" H. pylori antibody].

The LZ test "Eiken" for H. pylori antibody (LZ test) was examined. In patients with an antibody titer of ≥3.0U/mL and <10.0U/mL among 698 patients who underwent breath tests, the status of H. pylori infection was assessed from the results of the 13C urea breath test and the findings of gastric mucosal atrophy by performing an upper gastrointestinal endoscopy. A positive 13C urea breath test was observed in 22.3% of these patients (156/698, 95% confidence interval 19.4-25.6%), and gastric mucosal atrophy of C-2 or greater was observed in 39.7%. We presumed that 156 (22.3%) patients had present H. pylori infections, 141 (20.2%) patients had experienced a previous infection, and 401 (57.5%) patients were uninfected. The infection rate of H. pylori (current infection+previous infection) was treated as a so-called "risk of gastric cancer" and was 42.6% (297/698, 95% confidence interval 38.9-46.3%). In the LZ test, the concept of a negative high value should be understood. A receiver operating characteristic curve plotted depending on whether the 13C urea breath test was positive or not gave a positive cutoff value of 5.6U/mL;values greater than the cutoff value were taken as indicative of the need to investigate the status of H. pylori infection. Even without gastric mucosal atrophy, 2.0% of these patients had a positive breath test. For gastritis localized in the antrum (C-1), 17.8% of the patients had positive breath test results.