Effects of acid suppression and bismuth medications on the performance of diagnostic tests for Helicobacter pylori infection

Abstract OBJECTIVE: This study was designed to investigate whether acid suppression and bismuth medications interfere with the performance of diagnostic tests for Helicobacter pylori ( H. pylori ) infection. METHODS: Sixty patients with previous diagnoses of atrophic gastritis and H. pylori infection made in gastric biopsies taken at Hospital Departmental, Pasto, Colombia, were enrolled in the study. 13 C breath urea test (UBT) and stool antigen test (HpSA) were performed simultaneously. Two baseline tests were performed: one 7 days before and another the day before starting medications. A total of 20 patients received for 2 wk one of the following treatments: a) ranitidine; b) lansoprazole; or c) bismuth subsalicylate. The tests were repeated while the patients were on the prescribed medication on days 7 and 14 and then 2 wk after finishing the medication. RESULTS AND CONCLUSIONS: Utilizing standard cut-off values for the tests, our results indicate that in the case of the 13 C UBT test, ranitidine does not interfere with the results, whereas lansoprazole and bismuth may be expected to yield a significant proportion of false negative results (30–40% for lansoprazole and 45–55% for bismuth). In the case of the HpSA test, ranitidine does not interfere, whereas lansoprazole and bismuth may be expected to yield a nonsignificant proportion of false negative results (15–25% for lansoprazole and 10–15% for bismuth). Absolute values for both tests may be used to study the effects of the pharmacological agents on the characteristics of the infection.