Abstract:A rapid diagnostic system for Helicobacter pylori (H. pylori) was developed based on an urease analyser using a pH‐sensitive field effect transistor (pH‐FET). The system is composed of a solid‐phase capillary‐tube and a pH‐measuring cell. The solid‐phase tube, with an inner diameter 0.55 mm and coated with a monoclonal antibody against H. pylori's urease, was used to selectively capture the urease in endoscopically collected gastric mucus. The urease activity on the inner surface of the solid‐phase tube was measured by coupling it with ph‐FET in a pH measuring cell containing urea solution. Before immuno reaction in the solid‐phase, gastric mucus was diluted with a phosphate buffered saline containing 1% n‐octylglucoside, which was effective for accelerating the release of active urease from H. pylori's cells suspended in the sample solution. As a result of preliminary evaluations, it was found that the clinical sensitivity and specificity were 100 and 86%, respectively, using a bacteriological