Modified rapid urease test for Helicobacter pylori detection in relation to an immunohistochemical stain

Background: The rapid urease test and touch cytology have been used for the rapid detection of Helicobacter pylori infection. Recently, a modified rap id urease (MRU) test, which provides results in 20 min has been available o n a commercial basis. To date, few reports have evaluated the accuracy of t his test. This study evaluated the sensitivity, specificity, and accuracy o f the MRU test and touch cytology to detect H. pylori in relation to the de nsity of H. pylori infection determined semi-quantitatively by using immuno histochemical stains. Methods: Biopsy specimens obtained from a total of 60 patients who underwen t endoscopy for evaluation of gastroduodenal diseases were studied by using the MRU test, Giemsa stain for touch smear tissue and histological methods . An immunohistochemical stain was used as a standard, and the density of H . pylori infection was graded according to the number of individual bacteri a seen as follows: grade 0 = 0; grade 1+ = 1-9; grade 2+ = 10-29; grade 3= 30-99; grade 4+ greater than or equal to 100. The severity of gastritis w as evaluated histologically in each specimen and compared with the density of H. pylori infection. Results: The MRU test had an overall sensitivity of 73%, specificity of 100 % and accuracy of 85%. The Giemsa stain had a sensitivity of 91%, specifici ty of 100% and accuracy of 95%. The sensitivities of the MRU test and Giems a stain decreased in mild H. pylori infection. In the MRU test, the sensiti vity was 47% when the density of H. pylori infection was 1+, while 80-100% sensitivities were obtained when the densities of infection were greater th an or equal to 2+. With the Giemsa stain, the sensitivity was 80% when the density was 1+, while the sensitivity increased to 100% when the densities were greater than or equal to 2+. The severity of gastritis determined by t he Rauws scores showed a positive correlation with the density of H. pylori infection as evaluated by immunohistochemical staining. Conclusions: The MRU test had high sensitivity and specificity for moderate to severe H. pylori infection, but it may result in false-negative results in tests for mild infection. As the MRU test has the advantages of shorter incubation times and low cost, a combination of the MRU test and the Giems a stain for touch cytology may be the most time- and cost-efficient tests i n a clinical setting for the diagnosis of H. pylori infection. (C) 2000 Bla ckwell Science Asia Pty Ltd.