AIM: To compare the prevalence of Helicobacter pylori (H pylori) IgG and IgA antibodies between adult subjects, with defined gastric diseases, nondefined gastric disorders and those representing the population. METHODS: Data on H pylori IgG and IgA antibodies, determined by enzyme immunoassay, were analyzed in 3 252 subjects with DGD including 482 patients with gastric ulcer, 882 patients with duodenal ulcer, 1 525 patients with chronic gastritis only and 363 subjects with subsequent gastric cancer, 19 145 patients with NoDg and 4 854 POPUL subjects. The age-adjusted prevalences were calculated for 1-and 20-year age cohorts. RESULTS: The prevalences of IgG antibodies were equally high (89-96%) in all 20-year age cohorts of the DGD groups, whereas the prevalences of IgG antibodies were lower and increased by age in the POPUL and NoDg groups. The prevalences of IgA antibodies were also higher in the DGD groups; among them CA (84-89%) and GU groups (78-91%) showed significantly higher prevalences than DU (68-77%) and CG patients (59-74%) (OR 2.49, 95%CI 1.86-3.34 between the GU and DU groups). In the CA, GU, and DU groups, the IgA prevalences showed only minor variation according to age, while they increased by age in the CG, POPUL, and NoDg groups (P≤0.0001). The IgA response, but not the IgG response, was associated with an increased risk of CA (OR 2.41, 95%CI 1.79-3.53) and GU (OR 2.57, 95%CI 1.95-3.39) in comparison with CG patients. CONCLUSION: An IgA antibody response during H pylori infection is significantly more common in CA and GU patients as compared with CG patients. AIM: To compare the prevalence of Helicobacter pylori (H pylori) IgG and IgA antibodies between adult subjects, with defined gastric diseases, nondefined gastric disorders and those representing the population. METHODS: Data on H pylori IgG and IgA antibodies, determined by enzyme immunoassay , were analyzed in 3 252 subjects with DGD including 482 patients with gastric ulcer, 882 patients with duodenal ulcer, 1 525 patients with chronic gastritis only and 363 subjects with subsequent gastric cancer, 19 145 patients with NoDg and 4 854 POPUL subjects. The age -adjusted prevalence were calculated for 1-and 20-year age cohorts. RESULTS: The prevalences of IgG antibodies were equally high (89-96%) in all 20-year age cohorts of the DGD groups, whereas the prevalences of IgG antibodies were lower and increased by age in the POPUL and NoDg groups. The prevalences of IgA antibodies were also higher in the DGD groups; among them CA (84-89%) and GU groups (78-91%) showed significantly higher pre valences than DU (68-77%) and CG patients (59-74%) (OR 2.49, 95% CI 1.86-3.34 between the GU and DU groups). In the CA, GU, and DU groups, the IgA prevalences showed only minor variation according to age, while they increased by age in the CG, POPUL, and NoDg groups (P ≦ 0.0001). The IgA response, but not the IgG response, was associated with an increased risk of CA (OR 2.41, 95 CONCLUSION: An IgA antibody response during H pylori infection is significantly more common in CA and GU patients as compared with CG patients. (% CI 1.79-3.53) and GU (OR 2.57, 95% CI 1.95-3.39)