Diagnostic performance of immunohistochemistry and rapid urease test in detecting Helicobacter pylori, emphasizing bacterial localization and mucosal changes: a retrospective cross-sectional study.

Background: Accurate detection of Helicobacter pylori is essential for the diagnosis and management of gastritis and related gastrointestinal disorders. This study aimed to evaluate the diagnostic performance of the rapid urease test (RUT) and immunohistochemistry (IHC) using four antibodies (from BioGenex, Tokyo Medical and Dental University [TMDU], Cell Marque, and Dako), with a focus on bacterial localization (surface vs. subepithelial) and associated mucosal changes.

Methods: Gastric biopsy specimens from patients who underwent upper endoscopy at Vajira Hospital between June and December 2022 were retrospectively analyzed. Histological evaluations included hematoxylin and eosin staining, RUT, and IHC. The sensitivity of each antibody for detecting H. pylori was compared, with special attention paid to subepithelial colonization and histopathological patterns.

Results: The BioGenex antibody exhibited the highest sensitivity in detecting H. pylori, followed by TMDU, Cell Marque, and Dako antibodies. RUT demonstrated the lowest sensitivity, particularly in cases of chronic nonactive gastritis or minimal mucosal changes. Among the IHC antibodies, BioGenex detected the greatest number of subepithelial H. pylori cases, many of which were missed by the other antibodies and RUT. Subepithelial colonization typically presented as dot-like signals suggestive of coccoid forms or bacterial remnants. The BioGenex antibody identified all subepithelial cases detected by the TMDU antibody, highlighting the former's superior sensitivity. Statistical analysis confirmed the significantly higher diagnostic accuracy of the BioGenex antibody across multiple histological subgroups (p<0.05).

Conclusion: Subepithelial H. pylori colonization is clinically relevant and often undetected by RUT or less sensitive IHC antibodies. The BioGenex antibody was the most effective in identifying H. pylori in both surface and subepithelial regions. Patients with suspected subepithelial infection, particularly those without detectable surface bacteria, should undergo further evaluation using urea breath tests or stool antigen assays, in accordance with current clinical guidelines.