Performance of individual Helicobacter pylori antigens in the immunoblot-based detection of H. pylori infection.

To develop a specific line blot (LB) for supporting ELISA-based serodiagnosis of Helicobacter pylori infection, individual native/recombinant H. pylori antigens were evaluated with respect to their reactivity with both serum IgG and IgA from 156 dyspeptic screening patients (67% H. pylori positive). Of 13 antigens, HP0175, p17, and p19 revealed highest positive likelihood ratios for H. pylori-specific IgG (> 5.0) and were selected as LB substrates, in addition to the established virulence markers VacA and CagA. For validation, the LB was compared to a commercial whole-cell-lysate-based ELISA by parallel (re-)analysis of 156 screening sera, 22 sera from diabetes mellitus patients and 15 sera from follow-up patients after H. pylori eradication. In screening patients, the combined use of IgG ELISA and LB revealed a sensitivity, specificity, and accuracy of 94%, 81%, and 90%, respectively, whereas IgG ELISA alone exhibited a low specificity of 75%. In diabetic and follow-up patients, IgA ELISA exhibited high accuracy of 89% and 93%, respectively, whereas IgG detection was unreliable (accuracy < 80%). In conclusion, using HP0175, p17, p19, CagA, and VacA as LB substrates significantly improves the specificity of anti-H. pylori IgG analysis, providing a reliable tool for (1) confirmation/refutation of ELISA-based screening results and (2) assessment of the CagA/VacA status.