Long-term follow-up study of serum immunoglobulin G and immunoglobulin A antibodies after Helicobacter pylori eradication

Objective. There have been few studies concerning serum titers of anti-Heli cobacter pylori immunoglobulin G (IgG) antibody >12 months after eradicatio n of the original infection. Moreover, clinical usefulness of immunoglobuli n A (IgA) antibody levels remains to be established. The purpose of this st udy was to investigate long-term responses of serum IgG-specific and IgA-sp ecific antibodies to H pylori in children after eradication therapy. Study Design. A total of 34 children, 2 to 17 years of age (mean: 11.7 year s) with H pylori-associated gastroduodenal disease received eradication the rapy (proton pump inhibitor-based dual or triple regimens). Diagnoses inclu ded nodular gastritis (n = 8), gastric ulcer (n = 7), and duodenal ulcer (n = 19). Upper gastrointestinal endoscopy and biopsy were performed before t he therapy and at 1 to 2 months' posttreatment. H pylori infection and erad ication were defined by biopsy-based tests; eradication was successful in 2 8 patients and unsuccessful in 6. Pretreatment IgG was positive in 30 patie nts (88.2%), and the IgA was positive in 31 (91.2%), who were entered into this study (duration less than or equal to 24 months). Serum samples were o btained before treatment and at 1, 3, 6, 12, 18, and 24 months' posttreatme nt. IgG and IgA antibodies were measured using commercial enzyme immunoassa y kits (HM-CAP and PP-CAP; Enteric Products, Inc, New York, NY). Results. Compared with pretreatment values, IgG and IgA antibodies signific antly and steadily decreased at 1 through 24 months' posttreatment in succe ssfully treated patients. A decrease in titer of the IgA class was signific antly greater than that of the IgG class at 1 to 12 months' follow-up. Ther e was no significant decrease in titer of either antibody in all but 2 pati ents with eradication failure. A greater than or equal to 30% decrease in t iter of the IgA antibody at 6 months indicated eradication with sensitivity of 90.5% and specificity of 100%. For the IgG antibody, a 30% decrease at 12 months showed equal sensitivity and specificity. Seroreversion rates of IgG and IgA antibodies were 53%; and 48% at 12 months and were 86% and 81% at 24 months, respectively. The mean periods from the completion of eradica tion therapy to seroreversion of IgG and IgA antibodies were 11.2 +/- 7.0 a nd 11.6 +/- 7.8 months, respectively (not significantly different). A highe r pretreatment titer of Ige antibody was related to a longer period of sero reversion (r = 0.44). In one patient, C-13-urea breath test-confirmed reinf ection was accompanied by reappearance of significant titers of the IgG and IgA antibodies. Conclusions. A serology test is useful for evaluating eradication in childr en. Approximately half of patients with successful eradication remained to be IgG-seropositive and IgA-seropositive at 12 months' posttreatment When a decrease titer in antibody is used for assessing eradication, an endpoint of greater than or equal to 6 months is required. The IgA antibody may be a more convenient indicator of H pylori status than is the IgG antibody.