Helicobacter pylori in vivo diagnosis after food intake: Results of simultaneous [N-15]urea urine and [C-13]acetate breath tests

The protocols for C-13 and N-15 H. pylori tests stipulate that the diagnost ic agent should be taken on an empty stomach. It is presumed that food inta ke prior to the tests leads to less reliable test results due to a prolonga tion of the gastric residence time of the diagnostic agent urea. This might allow the bacteria to sprit a higher proportion of urea, resulting in an i ncreased number of false positives. 12 probands received 150 mg [N-15]urea and 75 mg sodium [C-13]acetate in 75 ml orange juice as a test drink. [N-15 ]Urea served as an agent to diagnose gastric H, pylori colonization. The 15 N tests were evaluated using a urine sample of the second hour after test s tart. [C-13]Acetate served as a marker of the gastric emptying of water-sol uble food including the urea under the influence of food intake. Breath air samples were taken to calculate the gastric emptying half life (EHL) and t he apparent resorption time (RT) of the urea. The double tests were carried out four times within four weeks using identical test protocols but differ ent standardized time periods of pretest fasting: overnight, two hours prio r to test, one hour prior to test, and no fasting at ail. The food intake a mount was standardized. Five probands testing positive in the overnight fasting test were also foun d to be positive in the other test variants with more or less empty stomach s. Seven other probands testing negative after overnight fasting tested neg ative in the other test variants as well. It is concluded that food intake prior to the test drink does not have much of an influence on the gastric residence time of urea and so on the qualit ative H. pylori test results. Due to identical behaviour of [C-13]urea and [N-15]urea in the stomach, this influence is believed to be independent on the labelling isotope. For survey purpose, no fasting conditions are requir ed for the H. pylori tests.