University of Southern California School of Medicine, Los Angeles 90033, USA.
BACKGROUND: Proton-pump inhibitor therapy may cause false-negative results on Helicobacter pylori diagnostic testing. OBJECTIVE: To determine the frequency and duration of conversion of urea breath test results from positive to negative in patients given a proton-pump inhibitor. SETTING: Two urban university gastroenterology clinics. PATIENTS: Patients infected with H. pylori who had positive results on urea breath tests. INTERVENTION: Lansoprazole, 30 mg/d for 28 days. MEASUREMENTS: The urea breath test was repeated at 28 days. If the results were negative, testing was repeated 3, 7, 14, and 28 days after completion of therapy until the results reverted to positive. RESULTS: 31 (33%) of 93 patients in whom H. pylori was not eradicated had a negative breath test result while receiving lansoprazole. The proportions of patients whose breath test results were positive after completion of lansoprazole therapy were 91% (95% CI, 83% to 96%) at 3 days, 97% (CI, 90% to 99%) at 7 days, and 100% (CI, 96% to 100%) at 14 days. CONCLUSION: Patients should not receive proton-pump inhibitors for 2 weeks before receiving the urea breath test for H. pylori infection.