Four-year trends in Helicobacter pylori IgG serology following successful eradication

Purpose: Detection of anti-Helicobacter pylori antibodies is accurate in the diagnosis of the infection, and there is a decline in IgG titers after successful eradication. It is not known whether these titers continue to decline during the next 3 to 4 years. Patients and Methods: Patients had been successfully treated for H pylori with triple therapy (metronidazole, tetracycline, and bismuth subsalicylate) during 1990 and 1991. Those who had frozen serum samples available from that time were contacted to have follow-up serum collected in 1994. A simultaneous [13C]urea breath test was done to confirm H pylori infection status. Serology was determined by quantitative enzyme-linked immunosorbent assay (ELISA) and qualitative immunoassay. Results: All 29 patients who agreed to participate were free of H pylori infection. They had a mean decrease in H pylori IgG titers of 51% from baseline (P<0.001). Titers remained stable from 1 year to a mean of 3.5 years after therapy (range 2.8 to 4.4). Of the 29 patients, 21 (72%) remained seropositive by ELISA 3.5 years after successful H pylori treatment, and 18 (62%) remained positive by rapid serum immunoassay. Conclusion: IgG titers against H pylori plateau at a 50% decrease after therapy. Helicobacter pylori serology, either quantitative or qualitative, will yield false positive results in patients who have previously been treated for H pylori and should not be used to determine infection status in this population.