Upfront immunohistochemistry improves specificity of Helicobacter pylori diagnosis. A French pathology laboratory point of view

Abstract Background There is no consensus about the histopathologic methods to detect Helicobacter pylori in gastric biopsies to date. We aimed to question about the value of upfront anti‐ H. pylori immunohistochemistry in this field. Material and Methods We led a retrospective study about the rate of H. pylori ‐positive gastric biopsies before and after the implementation of upfront immunohistochemistry, the inter‐rater and intermethods agreements in H. pylori identification about Hematoxylin‐Eosin Saffron ( HES ), Giemsa, and immunohistochemistry stains and the histopathologic features associated with low amounts of H. pylori . Results First, the rate of H. pylori ‐positive gastric biopsies significantly diminished after the implementation of upfront immunohistochemistry (from 21.15% to 12.56%, P <.0001), suggesting potential overdiagnosis of H. pylori infection before the use of immunohistochemistry. Secondly, immunohistochemistry was the most reproducible and performing stain (kappa values >0.80), but HES and Giemsa stains also presented good‐to‐very good agreements. Finally, less than 1% of gastric biopsies with inconspicuous H. pylori infection showed no mucosal injury pointing out that any HES ‐detected mucosal injury could help to preselect the gastric biopsies requiring ancillary stains for the detection of H. pylori . Conclusions Albeit being considered as a gold standard in the detection of H. pylori , the interest of using immunohistochemistry as an upfront stain on gastric biopsies is still debated. In our opinion, its use in second line in case of ambiguous HE / HES ‐Giemsa result is more appropriate. Further effort is needed to optimize the inexpensive but feasible HE / HES ‐based detection of H. pylori .