Immunoblotting using multiple antigens is essential to demonstrate the true risk of Helicobacter pylori infection for gastric cancer

Background Enzyme-linked immunosorbent assays (ELISAs) for detection of Helicobacter pylori infection, using IgG antibodies, may significantly underestimate the association with gastric cancer. Aim To compare associations between H. pylori and cardia (CGC) and noncardia gastric cancer (NCGC) using ELISA and immunoblotting and determine the effect of atrophic gastritis on detection. Methods Nested case-control study within the Melbourne Collaborative Cohort Study. Helicobacter pylori antibodies were detected in subjects with CGC (n = 18), NCGC (n = 34) and controls (n = 69 and 134 respectively) using ELISA (pylori DTect) and immunoblot (Helicoblot 2.1). Pepsinogen I levels were measured using ELISA. Results Using ELISA, H. pylori-positivity in the CGC group was 33% vs. 35% in controls [odds ratio (OR = 0.9, 95% CI: 0.3-2.7)], while that in the NCGC group was 79% vs. 63% in controls [OR = 2.3 (95% CI: 0.9-5.8)]. Based on immunoblotting, H. pylori-positivity in the CGC group was 44% vs. 39% in their controls [OR = 1.2 (95% CI: 0.4-3.4)], while that in the NCGC group was 94% vs. 63% in controls [OR = 10.6 (95% CI: 2.4-47.4)]. Pepsinogen I levels in the NCGC cases and controls showed the lowest median level (4 ng/mL) to be in subjects negative by ELISA but positive by immunoblotting. Conclusion Immunoblotting improves the accuracy of H. pylori studies involving gastric cancer.