PREMEDICATION WITH XYLOCAINE SPRAY DOES NOT LEAD TO A FALSE-POSITIVE RAPID UREASE TEST

Rapid urease tests are used for quick identification of Helicobacter p ylori during upper gastrointestinal endoscopy. Rapid urease test solut ions contain urea, which in the presence of H. pylori urease, generate s ammonia, which changes the test medium color to indicate a positive result. Theoretically, Xylocaine spray (ASTRA, Sodertalje, Sweden), wh ich has a basic pH value, could cause a similar positive reaction in t he test medium. To determine whether patients premedicated with Xyloca ine spray have a higher rate of false positive urease tests, we compar ed the results of a rapid urease test and histologic stains in 107 pat ients, 54 premedicated with Xylocaine spray and 53 premedicated with i ntravenous midazolam but not Xylocaine spray. There were no significan t differences in test sensitivity, specificity, or predictive values b etween the study groups. We conclude that patients can be premedicated with Xylocaine spray without concern that the false positive rate of rapid urease tests will increase.