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

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, Paste, Colombia, were enrolled in the study. C-13 breath urea test (UBT) a nd stool antigen test (HpSA) were performed simultaneously. Two baseline te sts were performed: one 7 days before and another the day before starting m edications. A total of 20 patients received for 2 wk one of the following t reatments: a) ranitidine; b) lansoprazole; or c) bismuth subsalicylate. The tests were repeated while the patients were on the prescribed medication o n days 7 and 14 and then 2 wk after finishing the medication. RESULTS AND CONCLUSIONS: Utilizing standard cut-off values for the tests, o ur results indicate that in the case of the C-13 UBT test, ranitidine does not interfere with the results, whereas lansoprazole and bismuth may be exp ected to yield a significant proportion of false negative results (30-40% f or lansoprazole and 45-55% for bismuth). In the case of the HpSA test, rani tidine 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 b e used to study the effects of the pharmacological agents on the characteri stics of the infection. (Am J Gastroenterol 1999;94:2380-2383. (C) 1999 by Am. Coll. of Gastroenterology).