Helicobacter pylori IgG ELISA

H. pylori is detectable in nearly 100% of adult patients with duodenal ulcer and about 80% of patients with gastric ulcer. An association between H. pylori and gastric cancer is confirmed. In developing countries, where most children become infected by the age of 10, gastric cancer rates are very high. In the USA and other developed countries, standards of hygiene and the increasing socioeconomic status of the population have reduced the incidence of infection, and in parallel, the rates of peptic ulcers and gastric cancer have declined. There is excellent correlation between the clinical presentation of gastritis, the presence of H. pylori in the stomach and elevated serum H. pylori IgG antibody. ELISA sensitivity and specificity are 90%, and the predictive value of a negative result for is very high. H. pylori-specific IgG antibody falls significantly after successful antibacterial therapy. Eradication of H. pylori is associated with a significant reduction in duodenal ulcer recurrence. H. pylori strains are classified into two broad groups – those that express both VacA and CagA (type I) and those that produce neither (type II). Type I strains are predominate in patients with ulcers and cancer. Up to 50% of adults is infected with H. pylori, but most of them are asymptotic and will not develop ulcer. The reason is they are infected with type II. 80-100% of patients with duodenal ulcer disease produce CagA antibodies against a 128 kd antigen compared with 60-63% of H. pylori-infected persons with gastritis only, indicating that serologic responses to the 128 kd protein are more prevalent among H. pyloriinfected persons with duodenal ulcers than infected persons without peptic ulceration. In H. pylori-infected patients who develop gastric cancer, serum IgG against CagA 94% sensitive and 93% specific, indicating that detection of antibodies to CagA is useful marker for diagnosis of duodenal ulcer and gastric cancer.