The Diagnostic Value of Enzyme Immunoassay and Immunoblot in Monitoring Eradication of Helicobacter pylori

55 patients with severe ulcer disease and H. pylori infection, successfully treated with antimicrobials, were followed-up with repeated blood samples for up to 32 months. Sera were analysed by enzyme immunoassay (EIA) for IgG and IgA antibodies and by IgG immunoblot. The EIA for IgG antibodies showed a high sensitivity (100%), while IgA antibodies above the cut-off level were found in 55% of the patients. At a median of 77 days after onset of treatment, approximately 50% of the patients showed a significant decrease (≥50%) of IgG or had titres below the cut-off level. All patients but 1 had a significant decrease of IgG after 6-12 months. The decrease was slower for IgA. The H. pylori-specific 116 kDa and 19.5 kDa bands were found in all pre-treatment samples, but the decrease in median intensity of the bands was slower than for the IgG EIA. In the 32-months post-treatment samples, both bands had an intensity still above 50% of the pre-treatment value. The study showed that the IgG EIA is a useful method for monitoring eradication of H. pylori. Immunoblot can detect previous H. pylori infection in EIA negative individuals.