Helicobacter pylori eradication decreases blood neutrophil and monocyte counts.

: The effect of Helicobacter pylori infection on systemic disorders is not well understood. : The purpose of this study was to elucidate the systemic effects of H. pylori infection by comparing differential counts of leukocytes and platelets in peripheral blood before and after eradication of H. pylori. : A total of 164 H. pylori-positive patients underwent eradication therapy, and populations of peripheral blood leukocytes and platelets before and 0 (just after therapy), 1, 3 and 12 months after eradication were retrospectively analysed. : In the eradicated group ( n = 138), blood leukocytes, neutrophils and monocytes decreased significantly after eradication, but there was no significant change in eosinophils, basophils, lymphocytes or platelets. In the non-eradicated group ( n = 26), there was no significant change in any studied parameter. With regard to smoking status, although leukocytes and neutrophils did not decrease after eradication in the smoking group, they significantly decreased after eradication in the nonsmoking group. : These findings suggest that: (1) H. pylori infection increases neutrophil and monocyte counts in the peripheral blood, which indicates a significant role of H. pylori infection in systemic disorders; and (2) Smoking may mask the effect of H. pylori eradication on peripheral leukocytes, which would explain the controversy in previous reports concerning H. pylori infection and peripheral leukocytes. [ABSTRACT FROM AUTHOR]