What does the absence of Helicobacter pylori from the antrum imply?

Helicobacter pylori is absent in the antrum of approximately 5, 25, and 35% of patients with duodenal ulcer, gastric ulcer, and non-ulcer dyspepsia respectively and in the majority of asymptomatic healthy subjects from the West. The absence of H. pylori from the antrum could result from failure of exposure to (Group A) or colonization by (Group B) or temporary (Group C) or permanent (Group D) clearance of H. pylori, after initial colonization. Marked differences in the incidence of absence of H. pylori in antrum of different age group of control subjects from the West and the developing nation (such as India) are discussed.