Objective: Since the discovery of Helicobacter pylori strains several diagnostic methods have become available to assess the relevant infection. Biopsy-based tests are still considered to be the reference method for diagnosing H. pylori infection and monitoring eradication treatment. This study was designed to test the reproducibility of the results among observers for reporting presence of H. pylori in biopsy samples by fluorescence in situ hybridization (FISH) method.

Materials and Methods: Two Independent observers blinded to the study tried to detect strains of H. pylori species. A total of 100 formalin-fixed paraffin-embedded gastric biopsies were used to test the presence of H. pylori by FISH method. Sectioned biopsies were air dried and hybridized using commercially available test system Seafast® H. pylori Combi Kit (Izinta, Hungary) according to the manufacturer's instructions. This test kit labels H. pylori with the green fluorescent stain and the slides were examined with a Nikon Eclips 80i microscope equipped with a standard fluorescence filter set. In order to improve assessment of minor degrees of alteration, a detailed histopathological classification which also provided numerical data for statistical analysis was used. The density of H. pylori colonization was graded as follows: 0, none; 1, mild; 2, moderate; 3, severe. The specimens which were insufficient in mucosal thickness for proper assessment were excluded from the study.

Results: H. pylori was detected in 59 and 48 patients by two different observers, respectively. The level of agreement in the assessment of H. pylori by FISH method was good with a κ value of 0.65 (95% CI 0.31-0.75). However, in 11% of our samples there was disagreement between the observers. Semiqu-antitative scoring of H. pylori revealed moderate reproducibility. The observer agreement was lover with κ 0.14 (95% CI non-significant) for specimens with mild H. pylori density.

Conclusion: FISH seems to be a reliable, cheap and rapid method for the alternative diagnosis of H.pylori in gastric biopsy specimens. However, evaluation of the slides under microscopy is subjective and requires experience.