This prospective Canadian pilot study assesses the platelet response rate in H. pylori positive and negative patients and evaluates potential mechanisms to explain response. Patients with ITP received H. pylori eradication therapy and platelet counts at day 56 were used to assess response. Gastric permeability, stool H. pylori antigen and serum CagA anti-body were done at baseline and at day 60. Twenty-two patients were enrolled with an overall response rate of 27% (6/22). The prevalence of H. pylori was 18% (4/22). Seventy-five percent of the H. pylori positive patients (3/4) achieved a response compared to 17% (3/18) of the H. pylori negative patients (P