Immunoperoxidase in the interpretation of discordant histologic and urease findings for Helicobacter pylori.

Azure A and methylene blue ("Diff-Quik," DQ) and tissue urease (U) tests are popular methods to diagnose Helicobacter pylori. These tests usually correlate well but sometimes produce discordant results. This study evaluates the DQ and U tests by comparing them with the immunoperoxidase reference method to resolve discordant results. DQ and U tests were performed on gastric biopsies. Results were tabulated as DQ(+)/U(+), DQ(+)/U(-), DQ(-)/U(+), and DQ(-)/U(-). Cases that were DQ(+)/U(+) were recorded as positive and not tested with immunoperoxidase. Cases that had discordant DQ/U results were tested by immunoperoxidase to resolve the discordance. Cases which were negative for both DQ/U were evaluated by immunoperoxidase to confirm the validity of DQ(1-)/U(-). The groups were compared with concordant results (DQ(1-)/U(-) group) and immunoperoxidase versus discordant DQ/U results and immunoperoxidase. There were 56 gastric biopsy specimens. Among all cases, 6 were DQ(+)/U(+). Of the remaining 50 cases, 38 were concordant DQ(-)/U(-), whereas 12 showed discordant DQ/U results. All 38 concordant DQ(-)/U(-) specimens were confirmed negative, 11 discordant DQ/U cases were confirmed negative, and 1 DQ(+)/U(-) specimen was confirmed positive by immunoperoxidase. Comparison of concordant versus discordant results was not statistically significant (P=0.10). Among all discordant DQ and U, 11/12 (92%) were confirmed negative by immunoperoxidase. Thus, both concordant negative results and discordant results can be considered negative. Such interpretation of discordant results might prevent unnecessary additional procedures or treatment.