4708 Immunological rapid urease test-a new diagnostic system for detecting helicobacter pylori-.

Abstract

Introduction: New diagnostic methods have been developed aiming at sensitive, specific and rapid detection of H. pylori. We established a new diagnostic system using a monoclonal antibody against H. pylori urease and pH sensor. Aim: To evaluate the sensitivity, specificity, positive predictive value and negative predictive value of the present system and to determine the calibration curve and detection limits the system. Methods: H. pylori urease adsorbed on a solid-phase tip coated with a monoclonal antibody against H. pylori urease after 15 min of incubation with a gastric mucus sample solution was measured by the pH change of the urea solution inside the tip.The detection limit of H. pylori urease using this system was determined and compared with that of the CLO test. Clinical evaluation of the system was performed in 155 patients. Histological examination, CLO test and culture were used as the standard tests. Results:The present system could detect 0.25 mIU/ml of H. pylori urease in less than 20 min. The sensitivity of the present system is superior to that of the CLO test by about two orders of magnitude. If a patient with at least one positive result in a standard test for H. pylori was considered to be positive, the sensitivity, specificity, positive predictive value and negative predictive value of the system were calculated as 95.2%, 98.9%, 98.4% and 96.8%, respectively.The present system had a significantly higher rate of determining the correct diagnosis than the CLO test and histological examination (McNemar's test, p=0.023 and p=0.027, respectively). However, ten of 19 H. pylori -positive cases with the pH change less than 0.1 were negative for at least one of the standard tests, whereas the present system could detect H. pylori correctly in all but for three of these 19 cases. The present system accurately determined H. pylori status in 75 of 76 patients (98.7% ) who had completed treatment. Conclusions: Immunological rapid urease test makes it possible to detect H. pylori within 20 min, and gives very high sensitivity and specificity, especially in the patients with low urease activity.