Effect of simethicone on the accuracy of the rapid urease test

OBJECTIVESimethicone, which is a principal ingredient in the defoaming agent used during gastroscopy, can inhibit the growth of Helicobacter pylori (MIC, 64–128 mg/l). This prospective study was designed to evaluate the in vivo and in vitro effects of simethicone on the accuracy of the rapid urease test (RUT). METHODSIn the in vivo study, three sets of gastric biopsies (two from the antrum, and one from the corpus) were taken from 75 patients. The first set was examined histologically, and the second set was used for the RUT (pre-simethicone RUT). Then, 25 ml simethicone (1200 mg/l) was introduced into the stomach for a contact time of 1 min. A third set of gastric biopsies was taken for the RUT (post-simethicone RUT). In the in vitro clinical study, 41 patients were recruited. The first set of gastric biopsies was used for the RUT (pre-incubation RUT). The second set was incubated in 1 ml of simethicone for 5 min before being used for the RUT (post-incubation RUT). In the spectrophotometric study, urease activity before and after incubation in simethicone for 5 min was quantified in 12 patients by measuring the absorbance at 560 nm. RESULTSReading at 15 min, the concordance rate between the pre-simethicone and post-simethicone RUT was 98%. In the in vitro clinical study, the concordance rate between the pre-incubation and post-incubation RUT was 97%. The spectophotometric study showed a significant reduction of 43% in urease activity after incubation in simethicone. CONCLUSIONThe application of a defoaming agent containing simethicone does not affect the accuracy of the RUT. However, simethicone modestly suppresses urea hydrolysis.