Quantitative correlation of Helicobacter pylori stool antigen (HpSA) test with 13C-urea breath test (13C-UBT) by the updated Sydney grading system of gastritis

Background/Aims: Helicobacter pylori (H. pylori) infection has a causative relationship with various gastrointestinal disorders. C-13-urea breath test and H. pylori stool antigen test are two valuable noninvasive tests for detecting H. pylori infection. Since the bacterial load of H. pylori in the stomach and the resulting severity of gastritis are important in validating the status of H. pylori infection, we would like to investigate the relative diagnostic accuracy of C-13-urea breath test and H. pylori stool antigen test with respect to the severity of gastritis. Methodology: The H. pylori statuses of 62 consecutive patients were evaluated by five tests, i.e., culture, histology, biopsy urease test, C-13-urea breath test, and H. pylori stool antigen test. Gastritis was graded by the updated Sydney system. H. pylori status was defined as positive when the culture was positive or the concordance of positivity of two of the other four tests. Results: Thirty-five patients (56%) were H. pylori positive. The accuracy of H. pylori stool antigen test and C-13-urea breath test were 92.6% and 100 respectively. There was a positive correlation between the level of Delta(13)CO(2) of the C-13-urea breath test and the optical density value of enzyme immunoassay of the H. pylori stool antigen test (Rho=0.758, P<0.001). Both the level of Delta(13)CO(2) of C-13-UBT and the optical density value of enzyme immunoassay of the H. pylori stool antigen test correlated well with the separate score of the density of H. pylori (P<0.001, each) and the inflammatory activity (each P<0.001). Conclusions: Both the C-13-urea breath test and H. pylori stool antigen test are effective non-invasive methods to detect the status of H. pylori infection with respect to correlation with the density of H. pylori and inflammatory activity of gastritis.