The influence of isolated doses of drugs, feeding and colonic bacterial ureolysis on urea breath test results

SUMMARY Background : Aim of this work was to improve standardization of the 13 C‐urea breath test ( 13 C‐UBT) by evaluating the effect of drug administration, feeding and colonic ureolysis on the UBT results. Methods : Three different studies were performed. First, a 13 C‐UBT was performed in 41 Helicobacter pylori infected subjects before and after 1 day of therapy with sucralfate (5 g), colloidal bismuth (600 mg), amoxycillin (2.5 g) or omeprazole (40 mg). Second, a 13 C‐UBT was performed in 10 H. pylori ‐positive patients after an overnight fast and repeated 2 h after lunch. Finally, a 13 C‐UBT was carried out in seven healthy volunteers, with breath sampling prolonged to 6 h to investigate colonic bacterial ureolysis. Results : Even a short course of drugs specific for H. pylori may result in a falsely negative 13 C‐UBT. Feeding does not interfere with the 13 C‐UBT in infected subjects. No significant 13 C‐urea breakdown by colonic bacteria is observed during the 13 C‐UBT when it is prolonged to 6 h. Conclusion : The 13 C‐urea breath test is a sensitive clinical tool for the non‐invasive diagnosis of H. pylori infection. It is unaffected by feeding or colonic ureolysis. However, false negative results are likely even after 1 day of therapy with bactericidal, ‘cytoprotective’ or antisecretory drugs.