DETECTION OF HELICOBACTER-PYLORI BY RAPID UREASE TESTS - IS BIOPSY SIZE A CRITICAL VARIABLE

Background: The variables responsible for false-positive and false-neg ative rapid urease tests are largely unexplored. Objectives: We compar ed the results of rapid urease testing with jumbo cup forceps (3.3 mm diameter) and tiny cup forceps (1.8 mm diameter) with two rapid urease tests. Methods: Antral biopsies were obtained. The order of forceps a nd rapid urease tests was randomized. Biopsies were also taken for Gen ta staining. Results: One hundred and two patients were studied; 59 ha d Helicobacter pylori infection. There were 22 false-negative tests (8 CLOtest, 16 hpfast) and 5 false-positive tests (3 CLOtest, 2 hpfast). All 5 false-positive tests were among those positive only in the seco nd 12 hours. There was no difference in results with the jumbo and tin y cup forceps. Five percent to nine percent (average, 6.6%; 95% confid ence interval, 4.4% to 9.6%) of tests with any of the combinations gav e an erroneous categorization of H. pylori status. There were no clini cal or statistical differences in H. pylori categorizations by CLOtest or hpfast. Conclusion: The diagnostic yield for detecting H. pylori i nfection by rapid urease tests is not adversely affected by small biop sy size, possibly because tiny biopsies obtain superficial tissue wher e H. pylori reside.