Comparative Diagnostic Performance of Monoclonal Antibody Immunohistochemistry and Modified Giemsa Staining for Helicobacter pylori Detection in Chronic Gastritis

Accurate detection of Helicobacter pylori is essential for the effective management of chronic gastritis. While Modified Giemsa (MG) staining is a common diagnostic tool, its sensitivity can be limited in cases with low bacterial density or atypical morphology, often leading to under-detection. This study aimed to evaluate the comparative diagnostic performance and bacterial density grading of monoclonal antibody immunohistochemistry (IHC) versus MG staining to establish a more precise diagnostic algorithm. This analytical observational study utilized a retrospective cross-sectional design, analyzing 100 gastric biopsy specimens from patients with chronic gastritis. Detection rates and bacterial density, graded according to the Updated Sydney System, were compared between MG and IHC using monoclonal anti-H. pylori antibodies. Monoclonal antibody IHC demonstrated a significantly higher detection rate (72%) compared to MG (65%; p = 0.016). Discordance analysis identified seven cases that were positive by IHC but missed by MG, typically representing low-density infections. Although overall inter-method agreement was "almost perfect" (Cohen’s kappa = 0.839), IHC staining resulted in a significant ordinal shift toward higher bacterial density grades compared to MG (p = 0.016), providing more accurate staging of the infection. Monoclonal antibody IHC is superior to Modified Giemsa for the detection of H. pylori, particularly in identifying cases with low bacterial density or compromised morphology. While MG remains a cost-effective primary screening tool, a stepwise approach is recommended: IHC should be prioritized as a mandatory confirmatory test when histological or clinical suspicion remains high despite a negative MG result.