Utility and limitations of a method for detecting Helicobacter pylori-specific antigens in the stool

Background Recently, a method for detecting Helicobacter pylori-specific antigens in the stool (HpSA) has been proposed to be useful clinically. The aim of this study was to determine the accuracy of HpSA for the diagnosis of H. pylori infection, including early assessment after eradication treatment, and the potential for quantitative evaluation of H. pylori in the stomach. Methods. The subjects were 85 patients with gastroduodenal disorders who underwent endoscopic examination. Of these, 36 were treated for eradication of H. pylori infection and reassessed 4-8 weeks after treatment. HpSA was tested by enzyme immunoassay. For the definitive diagnosis of H. pylori infection, biopsy specimens were taken endoscopically and examined by quantitative culture, rapid urease test, and immunohistostaining. In addition, serum antibody against H. pylori was tested before the eradication treatment and a C-13-urea breath test was conducted after treatment. The results of these reference tests were compared with those obtained by HpSA. Results. The sensitivity and specificity of HpSA were 90.4% and 100% before eradication treatment and 57.1% and 100% after the treatment. There was a positive correlation between the optical density of HpSA and the number of H. pylori bacilli evaluated by quantitative culture. Conclusions. The HpSA test is considered to be an accurate method for the diagnosis of H. pylori infection, with high specificity. However, there may be problems of false negativity if HpSA is used for the early assessment of treatment efficacy. Furthermore, HpSA is suggested to have potential for the quantitative evaluation of H. pylori status in the stomach.