Effect of gastric acid suppression on C-13-urea breath test: comparison ofranitidine with omeprazole

Background: The assessment of the effect of H-2 antagonists on the results of the urea breath test has produced controversial results. Aim: To assess whether standard doses of both omeprazole and H-2 blockers c an adversely influence the accuracy of the urea breath test. Methods: Sixty dyspeptic patients with ascertained Helicobacter pylori infe ction were recruited for this prospective, open study. They were randomized to receive either omeprazole 20 mg at 08:00 hours (n = 30) or ranitidine 3 00 mg at 22:00 hours (n = 30) for 14 days. The urea breath test was perform ed at baseline, on day 14, while patients were still taking the antisecreto ry drugs, and on day 21, 1 week after their cessation. Duplicate breath sam ples were collected after ingestion of 75 mg C-13-urea + citric acid. A del ta value > 5 parts per thousand was considered positive. Results: On day 14 the median delta values had declined, but not significan tly (P = 0.07) compared to baseline (13.79 vs. 22.39) with omeprazole, whil e they had increased (P = 0.27) with ranitidine (27.21 vs. 19.46). On the s ame day there were five out of 30 (17%) and five out of 28 (18%) false-nega tive results in the omeprazole and ranitidine groups, respectively. All the se cases became positive again on day 21. However, in eight cases treated w ith omeprazole and 13 treated with ranitidine, there was an increase of 14- day delta values compared to baseline. Conclusion: Our study shows that both omeprazole and ranitidine at standard doses are able to negatively affect the results of the urea breath test. T heir adverse effect resolves within 7 days of drug cessation and therefore the withdrawal of these drugs 7 days before testing seems to be sufficient to avoid false-negative results. The surprising finding that both antisecre tory drugs reduce delta values in one group and increase them in another gr oup of patients deserves further study.