The stool antigen test for detection of Helicobacter pylori after eradication therapy

Background: Current noninvasive tests to confirm the eradication of Helicobacter pylori must be performed 4 weeks or more after eradication therapy is completed. Objective: To determine whether the stool antigen test, a relatively new noninvasive test for H. pylori, administered at various times after eradication therapy correctly identifies persons with persistent H. pylori infection. Design: Prospective blinded study. Setting: Six clinical centers in the United States and Europe. Patients: 84 H. pylori-infected patients undergoing endoscopy for upper abdominal symptoms. Measurements: At baseline and on day 35 after the completion of triple eradication therapy, all patients underwent endoscopy with histologic examination, rapid urease test and culture, urea breath test, and a stool antigen test. The stool antigen test was also performed on days 3, 7, 15, 21, 28, and 35 after completion of therapy. Results: Compared with the gold-standard endoscopic tests on day 35 after antimicrobial therapy, the urea breath test had a sensitivity of 94% (95% CI, 71% to 100%) and a specificity of 100% (CI, 94% to 100%). The stool antigen test had a sensitivity of 94% (CI, 71% to 100%) and a specificity of 97% (CI, 89% to 100%). On day 7 after treatment, the stool antigen test was predictive of eradication (positive predictive value, 100% [CI, 69% to 100%]; negative predictive value, 91% [CI, 82% to 97%]). Conclusion: A positive result on the stool antigen test 7 days after completion of therapy identifies patients in whom eradication of H. pylori was unsuccessful.